InstCombine: Merge "(trunc x) == C1 & (and x, CA) == C2" into a single and+icmp.

This happens when GVN widens loads. Part of PR6627.

llvm-svn: 130405

1 files changed, 29 insertions, 0 deletions

diff --git a/llvm/test/Transforms/InstCombine/merge-icmp.ll b/llvm/test/Transforms/InstCombine/merge-icmp.ll
new file mode 100644
index 00000000000..00020b157e0
--- /dev/null
+++ b/llvm/test/Transforms/InstCombine/merge-icmp.ll
@@ -0,0 +1,29 @@
+; RUN: opt -S -instcombine < %s | FileCheck %s
+
+define i1 @test1(i16* %x) {
+  %load = load i16* %x, align 4
+  %trunc = trunc i16 %load to i8
+  %cmp1 = icmp eq i8 %trunc, 127
+  %and = and i16 %load, -256
+  %cmp2 = icmp eq i16 %and, 17664
+  %or = and i1 %cmp1, %cmp2
+  ret i1 %or
+; CHECK: @test1
+; CHECK-NEXT: load i16
+; CHECK-NEXT: icmp eq i16 %load, 17791
+; CHECK-NEXT: ret i1
+}
+
+define i1 @test2(i16* %x) {
+  %load = load i16* %x, align 4
+  %and = and i16 %load, -256
+  %cmp1 = icmp eq i16 %and, 32512
+  %trunc = trunc i16 %load to i8
+  %cmp2 = icmp eq i8 %trunc, 69
+  %or = and i1 %cmp1, %cmp2
+  ret i1 %or
+; CHECK: @test2
+; CHECK-NEXT: load i16
+; CHECK-NEXT: icmp eq i16 %load, 32581
+; CHECK-NEXT: ret i1
+}