Make $fp and $ra callee-saved registers and let PrologEpilogInserter handle

[oota-llvm.git] / lib / Target / README.txt

diff --git a/lib/Target/README.txt b/lib/Target/README.txt
index c345ce50c0e365a6ace66768ba4d0faab1fc0ffb..ffe3fa477b9eac6b7aeadbce171b6ed3d35b7ad8 100644 (file)
--- a/lib/Target/README.txt
+++ b/lib/Target/README.txt
@@ -2259,49 +2259,50 @@ icmp transform.
 
 //===---------------------------------------------------------------------===//
 
-We should optimize this:
+This code:
 
-  %tmp = load i16* %arrayidx, align 4, !tbaa !0
-  %A = trunc i16 %tmp to i8
-  %cmp = icmp eq i8 %A, 127
-  %B.mask = and i16 %tmp, -256
-  %cmp7 = icmp eq i16 %B.mask, 17664
-  %or.cond = and i1 %cmp, %cmp7
-  br i1 %or.cond, label %land.lhs.true9, label %if.end
+typedef struct {
+int f1:1;
+int f2:1;
+int f3:1;
+int f4:29;
+} t1;
 
-into:
+typedef struct {
+int f1:1;
+int f2:1;
+int f3:30;
+} t2;
 
-  %tmp = load i16* %arrayidx, align 4, !tbaa !0
-  %0 = icmp eq i16 %tmp, 17791
-  br i1 %0, label %land.lhs.true9, label %if.end
-
-with this patch:
-Index: InstCombine/InstCombineCompares.cpp
-===================================================================
---- InstCombine/InstCombineCompares.cpp        (revision 129500)
-+++ InstCombine/InstCombineCompares.cpp        (working copy)
-@@ -2506,6 +2506,18 @@
-         return &I;
-       }
-     }
-+    
-+    // Transform "icmp eq (trunc X), cst" to "icmp (and X, mask), cst"
-+    if (Op0->hasOneUse() && match(Op0, m_Trunc(m_Value(A))) &&
-+        isa<ConstantInt>(Op1)) {
-+      APInt MaskV = APInt::getLowBitsSet(A->getType()->getPrimitiveSizeInBits(),
-+                                      Op0->getType()->getPrimitiveSizeInBits());
-+      Value *Mask =
-+        Builder->CreateAnd(A, ConstantInt::get(A->getContext(), MaskV));
-+      return new ICmpInst(I.getPredicate(), Mask,
-+                          ConstantExpr::getZExt(cast<ConstantInt>(Op1),
-+                                                Mask->getType()));
-+    }
-   }
-   
-   {
+t1 s1;
+t2 s2;
+
+void func1(void)
+{
+s1.f1 = s2.f1;
+s1.f2 = s2.f2;
+}
+
+Compiles into this IR (on x86-64 at least):
 
+%struct.t1 = type { i8, [3 x i8] }
+@s2 = global %struct.t1 zeroinitializer, align 4
+@s1 = global %struct.t1 zeroinitializer, align 4
+define void @func1() nounwind ssp noredzone {
+entry:
+  %0 = load i32* bitcast (%struct.t1* @s2 to i32*), align 4
+  %bf.val.sext5 = and i32 %0, 1
+  %1 = load i32* bitcast (%struct.t1* @s1 to i32*), align 4
+  %2 = and i32 %1, -4
+  %3 = or i32 %2, %bf.val.sext5
+  %bf.val.sext26 = and i32 %0, 2
+  %4 = or i32 %3, %bf.val.sext26
+  store i32 %4, i32* bitcast (%struct.t1* @s1 to i32*), align 4
+  ret void
+}
 
-Not having this is blocking resolving PR6627.
+The two or/and's should be merged into one each.
 
 //===---------------------------------------------------------------------===//
 
+