enhance GVN to forward substitute a stored value to a load

(and load -> load) when the base pointers must alias but when
they are different types.  This occurs very very frequently in
176.gcc and other code that uses bitfields a lot.

llvm-svn: 82399

1 files changed, 119 insertions, 0 deletions

diff --git a/llvm/test/Transforms/GVN/rle.ll b/llvm/test/Transforms/GVN/rle.ll
new file mode 100644
index 00000000000..cd3a611128c
--- /dev/null
+++ b/llvm/test/Transforms/GVN/rle.ll
@@ -0,0 +1,119 @@
+; RUN: opt < %s -gvn -S | FileCheck %s
+
+; 32-bit little endian target.
+target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128"
+
+;; Trivial RLE test.
+define i32 @test0(i32 %V, i32* %P) {
+  store i32 %V, i32* %P
+
+  %A = load i32* %P
+  ret i32 %A
+; CHECK: @test0
+; CHECK: ret i32 %V
+}
+
+;;===----------------------------------------------------------------------===;;
+;; Store -> Load  and  Load -> Load forwarding where src and dst are different
+;; types, but where the base pointer is a must alias.
+;;===----------------------------------------------------------------------===;;
+
+;; i32 -> f32 forwarding.
+define float @coerce_mustalias1(i32 %V, i32* %P) {
+  store i32 %V, i32* %P
+   
+  %P2 = bitcast i32* %P to float*
+
+  %A = load float* %P2
+  ret float %A
+; CHECK: @coerce_mustalias1
+; CHECK-NOT: load
+; CHECK: ret float 
+}
+
+;; i32* -> float forwarding.
+define float @coerce_mustalias2(i32* %V, i32** %P) {
+  store i32* %V, i32** %P
+   
+  %P2 = bitcast i32** %P to float*
+
+  %A = load float* %P2
+  ret float %A
+; CHECK: @coerce_mustalias2
+; CHECK-NOT: load
+; CHECK: ret float 
+}
+
+;; float -> i32* forwarding.
+define i32* @coerce_mustalias3(float %V, float* %P) {
+  store float %V, float* %P
+   
+  %P2 = bitcast float* %P to i32**
+
+  %A = load i32** %P2
+  ret i32* %A
+; CHECK: @coerce_mustalias3
+; CHECK-NOT: load
+; CHECK: ret i32* 
+}
+
+;; i32 -> f32 load forwarding.
+define float @coerce_mustalias4(i32* %P, i1 %cond) {
+  %A = load i32* %P
+  br i1 %cond, label %T, label %T
+T:
+  %P2 = bitcast i32* %P to float*
+
+  %B = load float* %P2
+  ret float %B
+  
+F:
+  %X = bitcast i32 %A to float
+  ret float %X
+
+; CHECK: @coerce_mustalias4
+; CHECK: %A = load i32* %P
+; CHECK-NOT: load
+; CHECK: ret float
+; CHECK: F:
+}
+
+;; i32 -> i8 forwarding
+define i8 @coerce_mustalias5(i32 %V, i32* %P) {
+  store i32 %V, i32* %P
+   
+  %P2 = bitcast i32* %P to i8*
+
+  %A = load i8* %P2
+  ret i8 %A
+; CHECK: @coerce_mustalias5
+; CHECK-NOT: load
+; CHECK: ret i8
+}
+
+;; i64 -> float forwarding
+define float @coerce_mustalias6(i64 %V, i64* %P) {
+  store i64 %V, i64* %P
+   
+  %P2 = bitcast i64* %P to float*
+
+  %A = load float* %P2
+  ret float %A
+; CHECK: @coerce_mustalias6
+; CHECK-NOT: load
+; CHECK: ret float
+}
+
+;; i64 -> i8* (32-bit) forwarding
+define i8* @coerce_mustalias7(i64 %V, i64* %P) {
+  store i64 %V, i64* %P
+   
+  %P2 = bitcast i64* %P to i8**
+
+  %A = load i8** %P2
+  ret i8* %A
+; CHECK: @coerce_mustalias7
+; CHECK-NOT: load
+; CHECK: ret i8*
+}
+