[InstCombine] Drop samesign in InstCombine

[dtcxzyw]

Closes #112476.

[llvmbot]

@llvm/pr-subscribers-llvm-transforms

Author: Yingwei Zheng (dtcxzyw)

Changes

Closes #112476.

---

Full diff: https://github.com/llvm/llvm-project/pull/112480.diff

2 Files Affected:

• (modified) llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp (+1)
• (modified) llvm/test/Transforms/InstCombine/icmp.ll (+15)

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
index 7129499e0f8f9d..64e3f11f5837b4 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -1844,6 +1844,7 @@ Instruction *InstCombinerImpl::foldICmpAndConstConst(ICmpInst &Cmp,
                                                /*HasNUW=*/true),
                              One, Or->getName());
         Value *NewAnd = Builder.CreateAnd(A, NewOr, And->getName());
+        Cmp.setSameSign(false);
         return replaceOperand(Cmp, 0, NewAnd);
       }
     }
diff --git a/llvm/test/Transforms/InstCombine/icmp.ll b/llvm/test/Transforms/InstCombine/icmp.ll
index 5e80134b153be7..7cafb4885ff0ee 100644
--- a/llvm/test/Transforms/InstCombine/icmp.ll
+++ b/llvm/test/Transforms/InstCombine/icmp.ll
@@ -3203,6 +3203,21 @@ define i1 @icmp_and_or_lshr(i32 %x, i32 %y) {
   ret i1 %ret
 }
 
+define i1 @icmp_and_or_lshr_samesign(i32 %x, i32 %y) {
+; CHECK-LABEL: @icmp_and_or_lshr_samesign(
+; CHECK-NEXT:    [[SHF1:%.*]] = shl nuw i32 1, [[Y:%.*]]
+; CHECK-NEXT:    [[OR2:%.*]] = or i32 [[SHF1]], 1
+; CHECK-NEXT:    [[AND3:%.*]] = and i32 [[X:%.*]], [[OR2]]
+; CHECK-NEXT:    [[RET:%.*]] = icmp ne i32 [[AND3]], 0
+; CHECK-NEXT:    ret i1 [[RET]]
+;
+  %shf = lshr i32 %x, %y
+  %or = or i32 %shf, %x
+  %and = and i32 %or, 1
+  %ret = icmp samesign ne i32 %and, 0
+  ret i1 %ret
+}
+
 define <2 x i1> @icmp_and_or_lshr_vec(<2 x i32> %x, <2 x i32> %y) {
 ; CHECK-LABEL: @icmp_and_or_lshr_vec(
 ; CHECK-NEXT:    [[SHF:%.*]] = lshr <2 x i32> [[X:%.*]], [[Y:%.*]]

[nikic]

LGTM