Re-apply r238452, the bug was in clang and was fixed in r260567.

Original commit message:
[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.

Patch by Philip Pfaffe!

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

llvm-svn: 260612

1 files changed, 79 insertions, 0 deletions

diff --git a/llvm/test/Transforms/InstCombine/load-bitcast32.ll b/llvm/test/Transforms/InstCombine/load-bitcast32.ll
new file mode 100644
index 00000000000..b1c78a8a314
--- /dev/null
+++ b/llvm/test/Transforms/InstCombine/load-bitcast32.ll
@@ -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
+}
+