[llvm] r238452 - [InstCombine] Fold IntToPtr and PtrToInt into preceding loads.

[David Majnemer]

Author: majnemer
Date: Thu May 28 13:39:17 2015
New Revision: 238452

URL: http://llvm.org/viewvc/llvm-project?rev=238452&view=rev
Log:
[InstCombine] Fold IntToPtr and PtrToInt into preceding loads.

Currently we only fold a BitCast into a Load when the BitCast is its
only user.

Do the same for any no-op cast.

Differential Revision: http://reviews.llvm.org/D9152

Added:
    llvm/trunk/test/Transforms/InstCombine/load-bitcast32.ll
    llvm/trunk/test/Transforms/InstCombine/load-bitcast64.ll
Modified:
    llvm/trunk/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp

Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp?rev=238452&r1=238451&r2=238452&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp Thu May 28 13:39:17 2015
@@ -483,12 +483,17 @@ static Instruction *combineLoadToOperati
   }
 
   // Fold away bit casts of the loaded value by loading the desired type.
+  // We can do this for BitCastInsts as well as casts from and to pointer types,
+  // as long as those are noops (i.e., the source or dest type have the same
+  // bitwidth as the target's pointers).
   if (LI.hasOneUse())
-    if (auto *BC = dyn_cast<BitCastInst>(LI.user_back())) {
-      LoadInst *NewLoad = combineLoadToNewType(IC, LI, BC->getDestTy());
-      BC->replaceAllUsesWith(NewLoad);
-      IC.EraseInstFromFunction(*BC);
-      return &LI;
+    if (auto* CI = dyn_cast<CastInst>(LI.user_back())) {
+      if (CI->isNoopCast(DL)) {
+        LoadInst *NewLoad = combineLoadToNewType(IC, LI, CI->getDestTy());
+        CI->replaceAllUsesWith(NewLoad);
+        IC.EraseInstFromFunction(*CI);
+        return &LI;
+      }
     }
 
   // FIXME: We should also canonicalize loads of vectors when their elements are

Added: llvm/trunk/test/Transforms/InstCombine/load-bitcast32.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/load-bitcast32.ll?rev=238452&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/load-bitcast32.ll (added)
+++ llvm/trunk/test/Transforms/InstCombine/load-bitcast32.ll Thu May 28 13:39:17 2015
@@ -0,0 +1,79 @@
+; RUN: opt -instcombine -S < %s | FileCheck %s
+
+target datalayout = "p:32:32:32"
+
+
+define i64* @test1(i8* %x) {
+entry:
+; CHECK-LABEL: @test1(
+; CHECK: load i64, i64*
+; CHECK: ret
+  %a = bitcast i8* %x to i64*
+  %b = load i64, i64* %a
+  %c = inttoptr i64 %b to i64*
+
+  ret i64* %c
+}
+
+define i32* @test2(i8* %x) {
+entry:
+; CHECK-LABEL: @test2(
+; CHECK: load i32*, i32**
+; CHECK: ret
+  %a = bitcast i8* %x to i32*
+  %b = load i32, i32* %a
+  %c = inttoptr i32 %b to i32*
+
+  ret i32* %c
+}
+
+define i64* @test3(i8* %x) {
+entry:
+; CHECK-LABEL: @test3(
+; CHECK: load i64*, i64**
+; CHECK: ret
+  %a = bitcast i8* %x to i32*
+  %b = load i32, i32* %a
+  %c = inttoptr i32 %b to i64*
+
+  ret i64* %c
+}
+
+define i64 @test4(i8* %x) {
+entry:
+; CHECK-LABEL: @test4(
+; CHECK: load i32, i32*
+; CHECK: zext
+; CHECK: ret
+  %a = bitcast i8* %x to i64**
+  %b = load i64*, i64** %a
+  %c = ptrtoint i64* %b to i64
+
+  ret i64 %c
+}
+
+define i32 @test5(i8* %x) {
+entry:
+; CHECK-LABEL: @test5(
+; CHECK: load i32, i32*
+; CHECK: ret
+  %a = bitcast i8* %x to i32**
+  %b = load i32*, i32** %a
+  %c = ptrtoint i32* %b to i32
+
+  ret i32 %c
+}
+
+define i64 @test6(i8* %x) {
+entry:
+; CHECK-LABEL: @test6(
+; CHECK: load i32, i32*
+; CHECK: zext
+; CHECK: ret
+  %a = bitcast i8* %x to i32**
+  %b = load i32*, i32** %a
+  %c = ptrtoint i32* %b to i64
+
+  ret i64 %c
+}
+

Added: llvm/trunk/test/Transforms/InstCombine/load-bitcast64.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/load-bitcast64.ll?rev=238452&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/load-bitcast64.ll (added)
+++ llvm/trunk/test/Transforms/InstCombine/load-bitcast64.ll Thu May 28 13:39:17 2015
@@ -0,0 +1,78 @@
+; RUN: opt -instcombine -S < %s | FileCheck %s
+
+target datalayout = "p:64:64:64"
+
+
+define i64* @test1(i8* %x) {
+entry:
+; CHECK-LABEL: @test1(
+; CHECK: load i64*, i64**
+; CHECK: ret
+  %a = bitcast i8* %x to i64*
+  %b = load i64, i64* %a
+  %c = inttoptr i64 %b to i64*
+
+  ret i64* %c
+}
+
+define i32* @test2(i8* %x) {
+entry:
+; CHECK-LABEL: @test2(
+; CHECK: load i32, i32*
+; CHECK: ret
+  %a = bitcast i8* %x to i32*
+  %b = load i32, i32* %a
+  %c = inttoptr i32 %b to i32*
+
+  ret i32* %c
+}
+
+define i64* @test3(i8* %x) {
+entry:
+; CHECK-LABEL: @test3(
+; CHECK: load i32, i32*
+; CHECK: ret
+  %a = bitcast i8* %x to i32*
+  %b = load i32, i32* %a
+  %c = inttoptr i32 %b to i64*
+
+  ret i64* %c
+}
+
+define i64 @test4(i8* %x) {
+entry:
+; CHECK-LABEL: @test4(
+; CHECK: load i64, i64*
+; CHECK: ret
+  %a = bitcast i8* %x to i64**
+  %b = load i64*, i64** %a
+  %c = ptrtoint i64* %b to i64
+
+  ret i64 %c
+}
+
+define i32 @test5(i8* %x) {
+entry:
+; CHECK-LABEL: @test5(
+; CHECK: load i64, i64*
+; CHECK: trunc
+; CHECK: ret
+  %a = bitcast i8* %x to i32**
+  %b = load i32*, i32** %a
+  %c = ptrtoint i32* %b to i32
+
+  ret i32 %c
+}
+
+define i64 @test6(i8* %x) {
+entry:
+; CHECK-LABEL: @test6(
+; CHECK: load i64, i64*
+; CHECK: ret
+  %a = bitcast i8* %x to i32**
+  %b = load i32*, i32** %a
+  %c = ptrtoint i32* %b to i64
+
+  ret i64 %c
+}
+