...because the definition of %x does not dominate all of its - uses. The LLVM infrastructure provides a verification pass that may be used - to verify that an LLVM module is well formed. This pass is automatically run - by the parser after parsing input assembly and by the optimizer before it - outputs bitcode. The violations pointed out by the verifier pass indicate - bugs in transformation passes or input to the parser.
+because the definition of %x does not dominate all of its uses. The + LLVM infrastructure provides a verification pass that may be used to verify + that an LLVM module is well formed. This pass is automatically run by the + parser after parsing input assembly and by the optimizer before it outputs + bitcode. The violations pointed out by the verifier pass indicate bugs in + transformation passes or input to the parser.
@@ -457,7 +459,7 @@...and it also shows a convention that we follow in this document. When +
It also shows a convention that we follow in this document. When demonstrating instructions, we will follow an instruction with a comment that defines the type and name of value produced. Comments are shown in italic text.
@@ -482,24 +484,21 @@ the "hello world" module:; Declare the string constant as a global constant... -@.LC0 = internal constant [13 x i8] c"hello world\0A\00" ; [13 x i8]* ++; Declare the string constant as a global constant. +@.LC0 = internal constant [13 x i8] c"hello world\0A\00" ; [13 x i8]* ; External declaration of the puts function -declare i32 @puts(i8 *) ; i32(i8 *)* +declare i32 @puts(i8 *) ; i32(i8 *)* ; Definition of main function -define i32 @main() { ; i32()* - ; Convert [13 x i8]* to i8 *... - %cast210 = getelementptr [13 x i8]* @.LC0, i64 0, i64 0 ; i8 * +define i32 @main() { ; i32()* + ; Convert [13 x i8]* to i8 *... + %cast210 = getelementptr [13 x i8]* @.LC0, i64 0, i64 0 ; i8 * - ; Call puts function to write out the string to stdout... - call i32 @puts(i8 * %cast210) ; i32 - ret i32 0
}
+ ; Call puts function to write out the string to stdout. + call i32 @puts(i8 * %cast210) ; i32 + ret i32 0
}
__imp_ and the function or variable
name.Currently, only the following parameter attributes are defined:
-define void @f() gc "name" { ...
+define void @f() gc "name" { ... }
When constructing the data layout for a given target, LLVM starts with a @@ -1436,11 +1442,6 @@ Classifications -
Note that the code generator does not yet support large integer types to be - used as function return types. The specific limit on how large a return type - the code generator can currently handle is target-dependent; currently it's - often 64 bits for 32-bit targets and 128 bits for 64-bit targets.
- @@ -1572,17 +1573,12 @@ Classifications -Note that 'variable sized arrays' can be implemented in LLVM with a zero - length array. Normally, accesses past the end of an array are undefined in - LLVM (e.g. it is illegal to access the 5th element of a 3 element array). As - a special case, however, zero length arrays are recognized to be variable - length. This allows implementation of 'pascal style arrays' with the LLVM - type "{ i32, [0 x float]}", for example.
- -Note that the code generator does not yet support large aggregate types to be - used as function return types. The specific limit on how large an aggregate - return type the code generator can currently handle is target-dependent, and - also dependent on the aggregate element types.
+There is no restriction on indexing beyond the end of the array implied by + a static type (though there are restrictions on indexing beyond the bounds + of an allocated object in some cases). This means that single-dimension + 'variable sized array' addressing can be implemented in LLVM with a zero + length array type. An implementation of 'pascal style arrays' in LLVM could + use the type "{ i32, [0 x float]}", for example.
@@ -1620,16 +1616,16 @@ ClassificationsNote that the code generator does not yet support large aggregate types to be - used as function return types. The specific limit on how large an aggregate - return type the code generator can currently handle is target-dependent, and - also dependent on the aggregate element types.
- @@ -1771,8 +1762,7 @@ ClassificationsA vector type is a simple derived type that represents a vector of elements. Vector types are used when multiple primitive data are operated in parallel using a single instruction (SIMD). A vector type requires a size (number of - elements) and an underlying primitive data type. Vectors must have a power - of two length (1, 2, 4, 8, 16 ...). Vector types are considered + elements) and an underlying primitive data type. Vector types are considered first class.
Note that the code generator does not yet support large vector types to be - used as function return types. The specific limit on how large a vector - return type codegen can currently handle is target-dependent; currently it's - often a few times longer than a hardware vector register.
- @@ -2069,9 +2054,9 @@ Unsafe: For example, if "%X" has a zero bit, then the output of the 'and' operation will always be a zero, no matter what the corresponding bit from the undef is. As such, it is unsafe to optimize or assume that the result of the and is undef. -However, it is safe to assume that all bits of the undef could be 0, and -optimize the and to 0. Likewise, it is safe to assume that all the bits of -the undef operand to the or could be set, allowing the or to be folded to +However, it is safe to assume that all bits of the undef could be 0, and +optimize the and to 0. Likewise, it is safe to assume that all the bits of +the undef operand to the or could be set, allowing the or to be folded to -1.%A = xor undef, undef - + %B = undef %C = xor %B, %B @@ -2152,7 +2137,7 @@ does not execute at all. This allows us to delete the divide and all code after it: since the undefined operation "can't happen", the optimizer can assume that it occurs in dead code. - +a: store undef -> %X @@ -2164,7 +2149,7 @@ b: unreachableThese examples reiterate the fdiv example: a store "of" an undefined value -can be assumed to not have any effect: we can assume that the value is +can be assumed to not have any effect: we can assume that the value is overwritten with bits that happen to match what was already there. However, a store "to" an undefined location could clobber arbitrary memory, therefore, it has undefined behavior.
@@ -2181,7 +2166,7 @@ has undefined behavior.The 'blockaddress' constant computes the address of the specified basic block in the specified function, and always has an i8* type. Taking the address of the entry block is illegal.
- +This value only has defined behavior when used as an operand to the 'indirectbr' instruction or for comparisons against null. Pointer equality tests between labels addresses is undefined @@ -2190,7 +2175,7 @@ has undefined behavior.
pointer sized value as long as the bits are not inspected. This allows ptrtoint and arithmetic to be performed on these values so long as the original value is reconstituted before the indirectbr. - +Finally, some targets may provide defined semantics when using the value as the operand to an inline assembly, but that is target specific. @@ -2541,7 +2526,7 @@ Instructions
Note that the code generator does not yet fully support large - return values. The specific sizes that are currently supported are - dependent on the target. For integers, on 32-bit targets the limit - is often 64 bits, and on 64-bit targets the limit is often 128 bits. - For aggregate types, the current limits are dependent on the element - types; for example targets are often limited to 2 total integer - elements and 2 total floating-point elements.
- @@ -2726,7 +2703,7 @@ IfUnequal: rest of the arguments indicate the full set of possible destinations that the address may point to. Blocks are allowed to occur multiple times in the destination list, though this isn't particularly useful. - +This destination list is required so that dataflow analysis has an accurate understanding of the CFG.
@@ -3083,7 +3060,7 @@ InstructionThe two arguments to the 'mul' instruction must be integer or vector of integer values. Both arguments must have identical types.
- +The value produced is the integer product of the two operands.
@@ -3155,7 +3132,7 @@ InstructionThe 'udiv' instruction returns the quotient of its two operands.
The two arguments to the 'udiv' instruction must be +
The two arguments to the 'udiv' instruction must be integer or vector of integer values. Both arguments must have identical types.
@@ -3190,7 +3167,7 @@ InstructionThe 'sdiv' instruction returns the quotient of its two operands.
The two arguments to the 'sdiv' instruction must be +
The two arguments to the 'sdiv' instruction must be integer or vector of integer values. Both arguments must have identical types.
@@ -3261,7 +3238,7 @@ Instruction division of its two arguments.The two arguments to the 'urem' instruction must be +
The two arguments to the 'urem' instruction must be integer or vector of integer values. Both arguments must have identical types.
@@ -3301,7 +3278,7 @@ Instruction elements must be integers.The two arguments to the 'srem' instruction must be +
The two arguments to the 'srem' instruction must be integer or vector of integer values. Both arguments must have identical types.
@@ -3396,7 +3373,7 @@ InstructionBoth arguments to the 'shl' instruction must be the same integer or vector of integer type. 'op2' is treated as an unsigned value.
- +The value produced is op1 * 2op2 mod 2n, where n is the width of the result. If op2 @@ -3432,7 +3409,7 @@ Instruction operand shifted to the right a specified number of bits with zero fill.
Both arguments to the 'lshr' instruction must be the same +
Both arguments to the 'lshr' instruction must be the same integer or vector of integer type. 'op2' is treated as an unsigned value.
@@ -3472,7 +3449,7 @@ Instruction extension.Both arguments to the 'ashr' instruction must be the same +
Both arguments to the 'ashr' instruction must be the same integer or vector of integer type. 'op2' is treated as an unsigned value.
@@ -3512,7 +3489,7 @@ Instruction operands.The two arguments to the 'and' instruction must be +
The two arguments to the 'and' instruction must be integer or vector of integer values. Both arguments must have identical types.
@@ -3571,7 +3548,7 @@ Instruction two operands.The two arguments to the 'or' instruction must be +
The two arguments to the 'or' instruction must be integer or vector of integer values. Both arguments must have identical types.
@@ -3634,7 +3611,7 @@ Instruction complement" operation, which is the "~" operator in C.The two arguments to the 'xor' instruction must be +
The two arguments to the 'xor' instruction must be integer or vector of integer values. Both arguments must have identical types.
@@ -3682,7 +3659,7 @@ Instruction -
- <result> = shufflevector <4 x i32> %v1, <4 x i32> %v2,
+ <result> = shufflevector <4 x i32> %v1, <4 x i32> %v2,
<4 x i32> <i32 0, i32 4, i32 1, i32 5> ; yields <4 x i32>
- <result> = shufflevector <4 x i32> %v1, <4 x i32> undef,
+ <result> = shufflevector <4 x i32> %v1, <4 x i32> undef,
<4 x i32> <i32 0, i32 1, i32 2, i32 3> ; yields <4 x i32> - Identity shuffle.
- <result> = shufflevector <8 x i32> %v1, <8 x i32> undef,
+ <result> = shufflevector <8 x i32> %v1, <8 x i32> undef,
<4 x i32> <i32 0, i32 1, i32 2, i32 3> ; yields <4 x i32>
- <result> = shufflevector <4 x i32> %v1, <4 x i32> %v2,
+ <result> = shufflevector <4 x i32> %v1, <4 x i32> %v2,
<8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7 > ; yields <8 x i32>
-The 'zext' instruction zero extends its operand to type +
The 'zext' instruction zero extends its operand to type ty2.
The 'zext' instruction takes a value to cast, which must be of +
The 'zext' instruction takes a value to cast, which must be of integer type, and a type to cast it to, which must also be of integer type. The bit size of the - value must be smaller than the bit size of the destination type, + value must be smaller than the bit size of the destination type, ty2.
The 'sext' sign extends value to the type ty2.
The 'sext' instruction takes a value to cast, which must be of +
The 'sext' instruction takes a value to cast, which must be of integer type, and a type to cast it to, which must also be of integer type. The bit size of the - value must be smaller than the bit size of the destination type, + value must be smaller than the bit size of the destination type, ty2.
The 'fptrunc' instruction takes a floating point value to cast and a floating point type to cast it to. The size of value must be larger than the size of - ty2. This implies that fptrunc cannot be used to make a + ty2. This implies that fptrunc cannot be used to make a no-op cast.
The 'fptrunc' instruction truncates a value from a larger - floating point type to a smaller + floating point type to a smaller floating point type. If the value cannot fit within the destination type, ty2, then the results are undefined.
@@ -4381,7 +4358,7 @@ entry: floating point value.The 'fpext' instruction takes a +
The 'fpext' instruction takes a floating point value to cast, and a floating point type to cast it to. The source type must be smaller than the destination type.
@@ -4424,7 +4401,7 @@ entry: vector integer type with the same number of elements as tyThe 'fptoui' instruction converts its +
The 'fptoui' instruction converts its floating point operand into the nearest (rounding towards zero) unsigned integer value. If the value cannot fit in ty2, the results are undefined.
@@ -4450,7 +4427,7 @@ entry:The 'fptosi' instruction converts +
The 'fptosi' instruction converts floating point value to type ty2.
@@ -4462,7 +4439,7 @@ entry: vector integer type with the same number of elements as tyThe 'fptosi' instruction converts its +
The 'fptosi' instruction converts its floating point operand into the nearest (rounding towards zero) signed integer value. If the value cannot fit in ty2, the results are undefined.
@@ -4659,7 +4636,7 @@ entry:%X = bitcast i8 255 to i8 ; yields i8 :-1 %Y = bitcast i32* %x to sint* ; yields sint*:%x - %Z = bitcast <2 x int> %V to i64; ; yields i64: %V + %Z = bitcast <2 x int> %V to i64; ; yields i64: %V
To learn how to add an intrinsic function, please see the +
To learn how to add an intrinsic function, please see the Extending LLVM Guide.
@@ -6602,11 +6579,11 @@ LLVM.This intrinsic subtracts delta to the value stored in memory at +
This intrinsic subtracts delta to the value stored in memory at ptr. It yields the original value at ptr.
These intrinsics takes the signed or unsigned minimum or maximum of +
These intrinsics takes the signed or unsigned minimum or maximum of delta and the value stored in memory at ptr. It yields the original value at ptr.
@@ -7271,6 +7248,61 @@ LLVM. + + + ++ declare i32 @llvm.objectsize.i32( i8* <ptr>, i32 <type> ) + declare i64 @llvm.objectsize.i64( i8* <ptr>, i32 <type> ) ++ +
The llvm.objectsize intrinsic is designed to provide information + to the optimizers to either discover at compile time either a) when an + operation like memcpy will either overflow a buffer that corresponds to + an object, or b) to determine that a runtime check for overflow isn't + necessary. An object in this context means an allocation of a + specific type.
+ +The llvm.objectsize intrinsic takes two arguments. The first + argument is a pointer to the object ptr. The second argument + is an integer type which ranges from 0 to 3. The first bit in + the type corresponds to a return value based on whole objects, + and the second bit whether or not we return the maximum or minimum + remaining bytes computed.
+| 00 | +whole object, maximum number of bytes | +
| 01 | +partial object, maximum number of bytes | +
| 10 | +whole object, minimum number of bytes | +
| 11 | +partial object, minimum number of bytes | +
The llvm.objectsize intrinsic is lowered to either a constant + representing the size of the object concerned or i32/i64 -1 or 0 + (depending on the type argument if the size cannot be determined + at compile time.
+ +