[PatternMatch] Match commuted patterns in Signum_match (#121911)

Closes #121776.

Author: dtcxzyw

llvm/include/llvm/IR/PatternMatch.h

@@ -2870,7 +2870,7 @@ template <typename Opnd_t> struct Signum_match {
       return false;
 
     unsigned ShiftWidth = TypeSize - 1;
-    Value *OpL = nullptr, *OpR = nullptr;
+    Value *Op;
 
     // This is the representation of signum we match:
     //
@@ -2882,11 +2882,11 @@ template <typename Opnd_t> struct Signum_match {
     //
     // for i1 values.
 
-    auto LHS = m_AShr(m_Value(OpL), m_SpecificInt(ShiftWidth));
-    auto RHS = m_LShr(m_Neg(m_Value(OpR)), m_SpecificInt(ShiftWidth));
-    auto Signum = m_Or(LHS, RHS);
+    auto LHS = m_AShr(m_Value(Op), m_SpecificInt(ShiftWidth));
+    auto RHS = m_LShr(m_Neg(m_Deferred(Op)), m_SpecificInt(ShiftWidth));
+    auto Signum = m_c_Or(LHS, RHS);
 
-    return Signum.match(V) && OpL == OpR && Val.match(OpL);
+    return Signum.match(V) && Val.match(Op);
   }
 };
 

llvm/test/Transforms/InstCombine/compare-signs.ll

@@ -152,6 +152,19 @@ define i1 @test4a(i32 %a) {
   ret i1 %c
 }
 
+define i1 @test4a_commuted(i32 %a) {
+; CHECK-LABEL: @test4a_commuted(
+; CHECK-NEXT:    [[C:%.*]] = icmp slt i32 [[SIGNUM:%.*]], 1
+; CHECK-NEXT:    ret i1 [[C]]
+;
+  %l = ashr i32 %a, 31
+  %na = sub i32 0, %a
+  %r = lshr i32 %na, 31
+  %signum = or i32 %r, %l
+  %c = icmp slt i32 %signum, 1
+  ret i1 %c
+}
+
 define <2 x i1> @test4a_vec(<2 x i32> %a) {
 ; CHECK-LABEL: @test4a_vec(
 ; CHECK-NEXT:    [[C:%.*]] = icmp slt <2 x i32> [[A:%.*]], splat (i32 1)