[llvm] [ValueTracking][GlobalISel] UCMP and SCMP cannot create undef or poison (PR #154404)

[via llvm-commits]

https://github.com/AZero13 updated https://github.com/llvm/llvm-project/pull/154404

>From a42eb53e26a5d5b11894b86e36a0fca807d9a594 Mon Sep 17 00:00:00 2001
From: AZero13 <gfunni234 at gmail.com>
Date: Tue, 19 Aug 2025 11:55:53 -0400
Subject: [PATCH] [ValueTracking][GlobalISel] UCMP and SCMP cannot create undef
 or poison

They cannot make poison or undef, same for IR.
---
 llvm/lib/Analysis/ValueTracking.cpp           |  2 ++
 llvm/lib/CodeGen/GlobalISel/Utils.cpp         |  2 ++
 llvm/test/CodeGen/AArch64/freeze.ll           | 34 +++++++++++++++++++
 .../InstCombine/freeze-integer-intrinsics.ll  | 26 ++++++++++++++
 4 files changed, 64 insertions(+)

diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index 8ea3a03b1b4ab..21bdb2fbf6e56 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -7394,8 +7394,10 @@ static bool canCreateUndefOrPoison(const Operator *Op, UndefPoisonKind Kind,
       case Intrinsic::fshr:
       case Intrinsic::smax:
       case Intrinsic::smin:
+      case Intrinsic::scmp:
       case Intrinsic::umax:
       case Intrinsic::umin:
+      case Intrinsic::ucmp:
       case Intrinsic::ptrmask:
       case Intrinsic::fptoui_sat:
       case Intrinsic::fptosi_sat:
diff --git a/llvm/lib/CodeGen/GlobalISel/Utils.cpp b/llvm/lib/CodeGen/GlobalISel/Utils.cpp
index 8955dd0370539..e41fd81953f43 100644
--- a/llvm/lib/CodeGen/GlobalISel/Utils.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/Utils.cpp
@@ -1869,8 +1869,10 @@ static bool canCreateUndefOrPoison(Register Reg, const MachineRegisterInfo &MRI,
   case TargetOpcode::G_FSHR:
   case TargetOpcode::G_SMAX:
   case TargetOpcode::G_SMIN:
+  case TargetOpcode::G_SCMP:
   case TargetOpcode::G_UMAX:
   case TargetOpcode::G_UMIN:
+  case TargetOpcode::G_UCMP:
   case TargetOpcode::G_PTRMASK:
   case TargetOpcode::G_SADDO:
   case TargetOpcode::G_SSUBO:
diff --git a/llvm/test/CodeGen/AArch64/freeze.ll b/llvm/test/CodeGen/AArch64/freeze.ll
index d428b6aa483a7..36d88c5524932 100644
--- a/llvm/test/CodeGen/AArch64/freeze.ll
+++ b/llvm/test/CodeGen/AArch64/freeze.ll
@@ -429,3 +429,37 @@ define <8 x i16> @freeze_abds(<8 x i16> %a, <8 x i16> %b) {
   %r = add <8 x i16> %a, %f
   ret <8 x i16> %r
 }
+
+define i32 @freeze_scmp(i32 %a0) nounwind {
+; CHECK-LABEL: freeze_scmp:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    mov w8, #2 // =0x2
+; CHECK-NEXT:    cmp w8, w0
+; CHECK-NEXT:    cset w8, gt
+; CHECK-NEXT:    csinv w8, w8, wzr, ge
+; CHECK-NEXT:    cmp wzr, w8
+; CHECK-NEXT:    cset w8, gt
+; CHECK-NEXT:    csinv w0, w8, wzr, ge
+; CHECK-NEXT:    ret
+  %x = call i32 @llvm.scmp.i32(i32 2, i32 %a0)
+  %y = freeze i32 %x
+  %z = call i32 @llvm.scmp.i32(i32 0, i32 %y)
+  ret i32 %z
+}
+
+define i32 @freeze_ucmp(i32 %a0) nounwind {
+; CHECK-LABEL: freeze_ucmp:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    mov w8, #2 // =0x2
+; CHECK-NEXT:    cmp w8, w0
+; CHECK-NEXT:    cset w8, hi
+; CHECK-NEXT:    csinv w8, w8, wzr, hs
+; CHECK-NEXT:    cmp w8, #1
+; CHECK-NEXT:    cset w8, hi
+; CHECK-NEXT:    csinv w0, w8, wzr, hs
+; CHECK-NEXT:    ret
+  %x = call i32 @llvm.ucmp.i32(i32 2, i32 %a0)
+  %y = freeze i32 %x
+  %z = call i32 @llvm.ucmp.i32(i32 %y, i32 1)
+  ret i32 %z
+}
diff --git a/llvm/test/Transforms/InstCombine/freeze-integer-intrinsics.ll b/llvm/test/Transforms/InstCombine/freeze-integer-intrinsics.ll
index c4a590e1a12bf..3cab09c2876bf 100644
--- a/llvm/test/Transforms/InstCombine/freeze-integer-intrinsics.ll
+++ b/llvm/test/Transforms/InstCombine/freeze-integer-intrinsics.ll
@@ -426,6 +426,32 @@ define i1 @widenable_condition() {
   ret i1 %freeze
 }
 
+define i32 @freeze_scmp(i32 %a0) {
+; CHECK-LABEL: @freeze_scmp(
+; CHECK-NEXT:    [[A0_FR:%.*]] = freeze i32 [[A0:%.*]]
+; CHECK-NEXT:    [[X:%.*]] = call i32 @llvm.scmp.i32.i32(i32 2, i32 [[A0_FR]])
+; CHECK-NEXT:    [[Z:%.*]] = call i32 @llvm.scmp.i32.i32(i32 0, i32 [[X]])
+; CHECK-NEXT:    ret i32 [[Z]]
+;
+  %x = call i32 @llvm.scmp.i32(i32 2, i32 %a0)
+  %y = freeze i32 %x
+  %z = call i32 @llvm.scmp.i32(i32 0, i32 %y)
+  ret i32 %z
+}
+
+define i32 @freeze_ucmp(i32 %a0) {
+; CHECK-LABEL: @freeze_ucmp(
+; CHECK-NEXT:    [[A0_FR:%.*]] = freeze i32 [[A0:%.*]]
+; CHECK-NEXT:    [[X:%.*]] = call i32 @llvm.ucmp.i32.i32(i32 2, i32 [[A0_FR]])
+; CHECK-NEXT:    [[Z:%.*]] = call i32 @llvm.ucmp.i32.i32(i32 [[X]], i32 1)
+; CHECK-NEXT:    ret i32 [[Z]]
+;
+  %x = call i32 @llvm.ucmp.i32(i32 2, i32 %a0)
+  %y = freeze i32 %x
+  %z = call i32 @llvm.ucmp.i32(i32 %y, i32 1)
+  ret i32 %z
+}
+
 declare i32 @llvm.ctlz.i32(i32, i1 immarg)
 declare i32 @llvm.cttz.i32(i32, i1 immarg)
 declare i32 @llvm.abs.i32(i32, i1 immarg)