On 64-bit targets, change 32-bit getelementptr indices to be 64-bit

getelementptr indices, inserting an explicit cast if necessary.
This helps expose the sign-extension operation to other optimizations.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@56133 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index f02a7108fd6d7d5db7ca3c6c4dd2ff8fcd6f4f8d..1cb4fa2c213b66fe5bcc3c1776dec1e01c26b965 100644 (file)
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -9795,7 +9795,8 @@ Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
         }
       }
       // If we are using a wider index than needed for this platform, shrink it
-      // to what we need.  If the incoming value needs a cast instruction,
+      // to what we need.  If narrower, sign-extend it to what we need.
+      // If the incoming value needs a cast instruction,
       // insert it.  This explicit cast can make subsequent optimizations more
       // obvious.
       Value *Op = *i;
@@ -9809,6 +9810,16 @@ Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
           *i = Op;
           MadeChange = true;
         }
+      } else if (TD->getTypeSizeInBits(Op->getType()) < TD->getPointerSizeInBits()) {
+        if (Constant *C = dyn_cast<Constant>(Op)) {
+          *i = ConstantExpr::getSExt(C, TD->getIntPtrType());
+          MadeChange = true;
+        } else {
+          Op = InsertCastBefore(Instruction::SExt, Op, TD->getIntPtrType(),
+                                GEP);
+          *i = Op;
+          MadeChange = true;
+        }
       }
     }
   }

diff --git a/test/Transforms/InstCombine/getelementptr_promote.ll b/test/Transforms/InstCombine/getelementptr_promote.ll
new file mode 100644 (file)
index 0000000..811c5a9
--- /dev/null
+++ b/test/Transforms/InstCombine/getelementptr_promote.ll
@@ -0,0 +1,58 @@
+; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep getelementptr | grep {, i64}
+
+; Instcombine should promote the getelementptr index up to the target's
+; pointer size, making the conversion explicit, which helps expose it to
+; other optimizations.
+
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128"
+target triple = "x86_64-apple-darwin8"
+
+define i64 @test(i64* %first, i32 %count) nounwind {
+entry:
+       %first_addr = alloca i64*               ; <i64**> [#uses=2]
+       %count_addr = alloca i32                ; <i32*> [#uses=2]
+       %retval = alloca i64            ; <i64*> [#uses=2]
+       %n = alloca i32         ; <i32*> [#uses=5]
+       %result = alloca i64            ; <i64*> [#uses=4]
+       %0 = alloca i64         ; <i64*> [#uses=2]
+       %"alloca point" = bitcast i32 0 to i32          ; <i32> [#uses=0]
+       store i64* %first, i64** %first_addr
+       store i32 %count, i32* %count_addr
+       store i64 0, i64* %result, align 8
+       store i32 0, i32* %n, align 4
+       br label %bb1
+
+bb:            ; preds = %bb1
+       %1 = load i64** %first_addr, align 8            ; <i64*> [#uses=1]
+       %2 = load i32* %n, align 4              ; <i32> [#uses=1]
+       %3 = bitcast i32 %2 to i32              ; <i64> [#uses=1]
+       %4 = getelementptr i64* %1, i32 %3              ; <i64*> [#uses=1]
+       %5 = load i64* %4, align 8              ; <i64> [#uses=1]
+       %6 = lshr i64 %5, 4             ; <i64> [#uses=1]
+       %7 = load i64* %result, align 8         ; <i64> [#uses=1]
+       %8 = add i64 %6, %7             ; <i64> [#uses=1]
+       store i64 %8, i64* %result, align 8
+       %9 = load i32* %n, align 4              ; <i32> [#uses=1]
+       %10 = add i32 %9, 1             ; <i32> [#uses=1]
+       store i32 %10, i32* %n, align 4
+       br label %bb1
+
+bb1:           ; preds = %bb, %entry
+       %11 = load i32* %n, align 4             ; <i32> [#uses=1]
+       %12 = load i32* %count_addr, align 4            ; <i32> [#uses=1]
+       %13 = icmp slt i32 %11, %12             ; <i1> [#uses=1]
+       %14 = zext i1 %13 to i8         ; <i8> [#uses=1]
+       %toBool = icmp ne i8 %14, 0             ; <i1> [#uses=1]
+       br i1 %toBool, label %bb, label %bb2
+
+bb2:           ; preds = %bb1
+       %15 = load i64* %result, align 8                ; <i64> [#uses=1]
+       store i64 %15, i64* %0, align 8
+       %16 = load i64* %0, align 8             ; <i64> [#uses=1]
+       store i64 %16, i64* %retval, align 8
+       br label %return
+
+return:                ; preds = %bb2
+       %retval3 = load i64* %retval            ; <i64> [#uses=1]
+       ret i64 %retval3
+}