[llvm] goldsteinn/add nuw to or (PR #88088)
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Mon Apr 8 21:43:19 PDT 2024
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-llvm-transforms
Author: None (goldsteinn)
<details>
<summary>Changes</summary>
- **[InstCombine] Add tests for folding `(icmp eq/ne (add nuw x, y), 0)`; NFC**
- **[InstCombine] Fold `(icmp eq/ne (add nuw x, y), 0)` -> `(icmp eq/ne (or x, y), 0)`**
`(icmp eq/ne (or x, y), 0)` is probably easier to analyze than `(icmp
eq/ne x, -y)`
Proof: https://alive2.llvm.org/ce/z/2-VTb6
---
Full diff: https://github.com/llvm/llvm-project/pull/88088.diff
2 Files Affected:
- (modified) llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp (+5)
- (modified) llvm/test/Transforms/InstCombine/icmp-add.ll (+39-24)
``````````diff
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
index db302d7e526844..53aa84d53f3085 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -3453,6 +3453,11 @@ Instruction *InstCombinerImpl::foldICmpBinOpEqualityWithConstant(
if (Value *NegVal = dyn_castNegVal(BOp0))
return new ICmpInst(Pred, NegVal, BOp1);
if (BO->hasOneUse()) {
+ // (add nuw A, B) != 0 -> (or A, B) != 0
+ if (match(BO, m_NUWAdd(m_Value(), m_Value()))) {
+ Value *Or = Builder.CreateOr(BOp0, BOp1);
+ return new ICmpInst(Pred, Or, Constant::getNullValue(BO->getType()));
+ }
Value *Neg = Builder.CreateNeg(BOp1);
Neg->takeName(BO);
return new ICmpInst(Pred, BOp0, Neg);
diff --git a/llvm/test/Transforms/InstCombine/icmp-add.ll b/llvm/test/Transforms/InstCombine/icmp-add.ll
index b99ed20d7d431c..e71a3af4b5be4f 100644
--- a/llvm/test/Transforms/InstCombine/icmp-add.ll
+++ b/llvm/test/Transforms/InstCombine/icmp-add.ll
@@ -9,10 +9,8 @@ declare void @use(i32)
define i1 @cvt_icmp_0_zext_plus_zext_eq_i16(i16 %arg, i16 %arg1) {
; CHECK-LABEL: @cvt_icmp_0_zext_plus_zext_eq_i16(
; CHECK-NEXT: bb:
-; CHECK-NEXT: [[I:%.*]] = zext i16 [[ARG:%.*]] to i32
-; CHECK-NEXT: [[I2:%.*]] = zext i16 [[ARG1:%.*]] to i32
-; CHECK-NEXT: [[I3:%.*]] = sub nsw i32 0, [[I]]
-; CHECK-NEXT: [[I4:%.*]] = icmp eq i32 [[I2]], [[I3]]
+; CHECK-NEXT: [[TMP0:%.*]] = or i16 [[ARG1:%.*]], [[ARG:%.*]]
+; CHECK-NEXT: [[I4:%.*]] = icmp eq i16 [[TMP0]], 0
; CHECK-NEXT: ret i1 [[I4]]
;
bb:
@@ -27,10 +25,8 @@ bb:
define i1 @cvt_icmp_0_zext_plus_zext_eq_i8(i8 %arg, i8 %arg1) {
; CHECK-LABEL: @cvt_icmp_0_zext_plus_zext_eq_i8(
; CHECK-NEXT: bb:
-; CHECK-NEXT: [[I:%.*]] = zext i8 [[ARG:%.*]] to i32
-; CHECK-NEXT: [[I2:%.*]] = zext i8 [[ARG1:%.*]] to i32
-; CHECK-NEXT: [[I3:%.*]] = sub nsw i32 0, [[I]]
-; CHECK-NEXT: [[I4:%.*]] = icmp eq i32 [[I2]], [[I3]]
+; CHECK-NEXT: [[TMP0:%.*]] = or i8 [[ARG1:%.*]], [[ARG:%.*]]
+; CHECK-NEXT: [[I4:%.*]] = icmp eq i8 [[TMP0]], 0
; CHECK-NEXT: ret i1 [[I4]]
;
bb:
@@ -1802,22 +1798,17 @@ define i1 @test4(i32 %a) {
ret i1 %c
}
-define { i32, i1 } @test4multiuse(i32 %a) {
-; CHECK-LABEL: @test4multiuse(
-; CHECK-NEXT: [[B:%.*]] = add nsw i32 [[A:%.*]], -2147483644
-; CHECK-NEXT: [[C:%.*]] = icmp slt i32 [[A]], 2147483640
-; CHECK-NEXT: [[TMP:%.*]] = insertvalue { i32, i1 } undef, i32 [[B]], 0
-; CHECK-NEXT: [[RES:%.*]] = insertvalue { i32, i1 } [[TMP]], i1 [[C]], 1
-; CHECK-NEXT: ret { i32, i1 } [[RES]]
+define {
+i32, i1 } @test4multiuse(i32 %a) {
;
- %b = add nsw i32 %a, -2147483644
- %c = icmp slt i32 %b, -4
+%b = add nsw i32 %a, -2147483644
+%c = icmp slt i32 %b, -4
- %tmp = insertvalue { i32, i1 } undef, i32 %b, 0
- %res = insertvalue { i32, i1 } %tmp, i1 %c, 1
+%tmp = insertvalue { i32, i1 } undef, i32 %b, 0
+%res = insertvalue { i32, i1 } %tmp, i1 %c, 1
- ret { i32, i1 } %res
+ret { i32, i1 } %res
}
define <2 x i1> @test4vec(<2 x i32> %a) {
@@ -2857,7 +2848,7 @@ define i1 @icmp_add_add_C_comm2(i32 %X, i32 %b) {
; CHECK-NEXT: [[CMP:%.*]] = icmp ugt i32 [[A]], [[TMP1]]
; CHECK-NEXT: ret i1 [[CMP]]
;
- %a = udiv i32 42, %X ; thwart complexity-based canonicalization
+ %a = udiv i32 42, %X ; thwart complexity-based canonicalization
%add1 = add i32 %a, %b
%add2 = add i32 %add1, -1
%cmp = icmp ugt i32 %a, %add2
@@ -2871,7 +2862,7 @@ define i1 @icmp_add_add_C_comm2_pred(i32 %X, i32 %b) {
; CHECK-NEXT: [[CMP:%.*]] = icmp ule i32 [[A]], [[TMP1]]
; CHECK-NEXT: ret i1 [[CMP]]
;
- %a = udiv i32 42, %X ; thwart complexity-based canonicalization
+ %a = udiv i32 42, %X ; thwart complexity-based canonicalization
%add1 = add i32 %a, %b
%add2 = add i32 %add1, -1
%cmp = icmp ule i32 %a, %add2
@@ -2886,7 +2877,7 @@ define i1 @icmp_add_add_C_comm2_wrong_pred(i32 %X, i32 %b) {
; CHECK-NEXT: [[CMP:%.*]] = icmp ult i32 [[A]], [[ADD2]]
; CHECK-NEXT: ret i1 [[CMP]]
;
- %a = udiv i32 42, %X ; thwart complexity-based canonicalization
+ %a = udiv i32 42, %X ; thwart complexity-based canonicalization
%add1 = add i32 %a, %b
%add2 = add i32 %add1, -1
%cmp = icmp ult i32 %a, %add2
@@ -2900,7 +2891,7 @@ define i1 @icmp_add_add_C_comm3(i32 %X, i32 %b) {
; CHECK-NEXT: [[CMP:%.*]] = icmp ugt i32 [[A]], [[TMP1]]
; CHECK-NEXT: ret i1 [[CMP]]
;
- %a = udiv i32 42, %X ; thwart complexity-based canonicalization
+ %a = udiv i32 42, %X ; thwart complexity-based canonicalization
%add1 = add i32 %b, %a
%add2 = add i32 %add1, -1
%cmp = icmp ugt i32 %a, %add2
@@ -3003,4 +2994,28 @@ define i1 @icmp_dec_notnonzero(i8 %x) {
ret i1 %c
}
+define i1 @icmp_addnuw_nonzero(i8 %x, i8 %y) {
+; CHECK-LABEL: @icmp_addnuw_nonzero(
+; CHECK-NEXT: [[TMP1:%.*]] = or i8 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT: [[C:%.*]] = icmp eq i8 [[TMP1]], 0
+; CHECK-NEXT: ret i1 [[C]]
+;
+ %i = add nuw i8 %x, %y
+ %c = icmp eq i8 %i, 0
+ ret i1 %c
+}
+
+define i1 @icmp_addnuw_nonzero_fail_multiuse(i32 %x, i32 %y) {
+; CHECK-LABEL: @icmp_addnuw_nonzero_fail_multiuse(
+; CHECK-NEXT: [[I:%.*]] = add nuw i32 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT: [[C:%.*]] = icmp eq i32 [[I]], 0
+; CHECK-NEXT: call void @use(i32 [[I]])
+; CHECK-NEXT: ret i1 [[C]]
+;
+ %i = add nuw i32 %x, %y
+ %c = icmp eq i32 %i, 0
+ call void @use(i32 %i)
+ ret i1 %c
+}
+
declare void @llvm.assume(i1)
``````````
</details>
https://github.com/llvm/llvm-project/pull/88088
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