[llvm-branch-commits] [llvm] release/19.x: [X86] Fix missing check of rotate <-> shift equivilence (Issue 108722) (PR #108783)

[via llvm-branch-commits]

https://github.com/llvmbot created https://github.com/llvm/llvm-project/pull/108783

Backport 1c378d2b145578948942512f9d6985e37659d013 81279bf97f187eee0446af00d8ae9ec32a22e878

Requested by: @goldsteinn

>From 4c558a8d535a48d0588671d1574bc5a70478adce Mon Sep 17 00:00:00 2001
From: Noah Goldstein <goldstein.w.n at gmail.com>
Date: Sun, 15 Sep 2024 09:00:28 -0700
Subject: [PATCH 1/2] [X86] Add test for issue 108722; NFC

(cherry picked from commit 1c378d2b145578948942512f9d6985e37659d013)
---
 llvm/test/CodeGen/X86/cmp-shiftX-maskX.ll | 24 +++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/llvm/test/CodeGen/X86/cmp-shiftX-maskX.ll b/llvm/test/CodeGen/X86/cmp-shiftX-maskX.ll
index 67070b989786db..799b5417857575 100644
--- a/llvm/test/CodeGen/X86/cmp-shiftX-maskX.ll
+++ b/llvm/test/CodeGen/X86/cmp-shiftX-maskX.ll
@@ -994,6 +994,30 @@ define i1 @shr_to_rotate_eq_i32_s5(i32 %x) {
   ret i1 %r
 }
 
+define i32 @issue108722(i32 %0) {
+; CHECK-NOBMI-LABEL: issue108722:
+; CHECK-NOBMI:       # %bb.0:
+; CHECK-NOBMI-NEXT:    movzbl %dil, %ecx
+; CHECK-NOBMI-NEXT:    shrl $24, %edi
+; CHECK-NOBMI-NEXT:    xorl %eax, %eax
+; CHECK-NOBMI-NEXT:    cmpl %edi, %ecx
+; CHECK-NOBMI-NEXT:    sete %al
+; CHECK-NOBMI-NEXT:    retq
+;
+; CHECK-BMI2-LABEL: issue108722:
+; CHECK-BMI2:       # %bb.0:
+; CHECK-BMI2-NEXT:    rorxl $8, %edi, %ecx
+; CHECK-BMI2-NEXT:    xorl %eax, %eax
+; CHECK-BMI2-NEXT:    cmpl %edi, %ecx
+; CHECK-BMI2-NEXT:    sete %al
+; CHECK-BMI2-NEXT:    retq
+  %2 = tail call i32 @llvm.fshl.i32(i32 %0, i32 %0, i32 24)
+  %3 = icmp eq i32 %2, %0
+  %4 = zext i1 %3 to i32
+  ret i32 %4
+}
+
+
 ;; NOTE: These prefixes are unused and the list is autogenerated. Do not add tests below this line:
 ; CHECK-AVX: {{.*}}
 ; CHECK-NOBMI-SSE2: {{.*}}

>From 7aaa237104f50ba921d05a371be00636ed700e14 Mon Sep 17 00:00:00 2001
From: Noah Goldstein <goldstein.w.n at gmail.com>
Date: Sun, 15 Sep 2024 09:00:34 -0700
Subject: [PATCH 2/2] [X86] Fix missing check of rotate <-> shift equivilence
 (Issue 108722)

Previous code was checking that rotate and shift where equivilent when
transforming shift -> rotate but not the other way around.

Closes #108767

(cherry picked from commit 81279bf97f187eee0446af00d8ae9ec32a22e878)
---
 llvm/lib/Target/X86/X86ISelLowering.cpp   | 2 +-
 llvm/test/CodeGen/X86/cmp-shiftX-maskX.ll | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index 5a9d679d7002cb..45989bcd07d37e 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -3415,7 +3415,7 @@ unsigned X86TargetLowering::preferedOpcodeForCmpEqPiecesOfOperand(
 
   // We prefer rotate for vectors of if we won't get a zext mask with SRL
   // (PreferRotate will be set in the latter case).
-  if (PreferRotate || VT.isVector())
+  if (PreferRotate || !MayTransformRotate || VT.isVector())
     return ShiftOpc;
 
   // Non-vector type and we have a zext mask with SRL.
diff --git a/llvm/test/CodeGen/X86/cmp-shiftX-maskX.ll b/llvm/test/CodeGen/X86/cmp-shiftX-maskX.ll
index 799b5417857575..227de9ad0ab690 100644
--- a/llvm/test/CodeGen/X86/cmp-shiftX-maskX.ll
+++ b/llvm/test/CodeGen/X86/cmp-shiftX-maskX.ll
@@ -997,8 +997,8 @@ define i1 @shr_to_rotate_eq_i32_s5(i32 %x) {
 define i32 @issue108722(i32 %0) {
 ; CHECK-NOBMI-LABEL: issue108722:
 ; CHECK-NOBMI:       # %bb.0:
-; CHECK-NOBMI-NEXT:    movzbl %dil, %ecx
-; CHECK-NOBMI-NEXT:    shrl $24, %edi
+; CHECK-NOBMI-NEXT:    movl %edi, %ecx
+; CHECK-NOBMI-NEXT:    roll $24, %ecx
 ; CHECK-NOBMI-NEXT:    xorl %eax, %eax
 ; CHECK-NOBMI-NEXT:    cmpl %edi, %ecx
 ; CHECK-NOBMI-NEXT:    sete %al