[llvm] 08c0857 - [InstCombine] cttz(sext(x)) -> cttz(zext(x))
Dávid Bolvanský via llvm-commits
llvm-commits at lists.llvm.org
Mon May 3 14:59:41 PDT 2021
Author: Dávid Bolvanský
Date: 2021-05-03T23:59:30+02:00
New Revision: 08c08577f94fd7efd2a670d0e5c3c6f72882fa0a
URL: https://github.com/llvm/llvm-project/commit/08c08577f94fd7efd2a670d0e5c3c6f72882fa0a
DIFF: https://github.com/llvm/llvm-project/commit/08c08577f94fd7efd2a670d0e5c3c6f72882fa0a.diff
LOG: [InstCombine] cttz(sext(x)) -> cttz(zext(x))
```
----------------------------------------
define i32 @src(i16 %x, i1 %b) {
%0:
%z = sext i16 %x to i32
%p = cttz i32 %z, %b
ret i32 %p
}
=>
define i32 @tgt(i16 %x, i1 %b) {
%0:
%z = zext i16 %x to i32
%p = cttz i32 %z, %b
ret i32 %p
}
Transformation seems to be correct!
```
https://alive2.llvm.org/ce/z/evomeg
Reviewed By: spatel
Differential Revision: https://reviews.llvm.org/D101764
Added:
Modified:
llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
llvm/test/Transforms/InstCombine/cttz.ll
Removed:
################################################################################
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
index 15740bb410e6..b2e173dec9fe 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -439,6 +439,14 @@ static Instruction *foldCttzCtlz(IntrinsicInst &II, InstCombinerImpl &IC) {
if (match(Op0, m_Neg(m_Value(X))))
return IC.replaceOperand(II, 0, X);
+ // cttz(sext(x)) -> cttz(zext(x))
+ if (match(Op0, m_OneUse(m_SExt(m_Value(X))))) {
+ auto *Zext = IC.Builder.CreateZExt(X, II.getType());
+ auto *CttzZext =
+ IC.Builder.CreateBinaryIntrinsic(Intrinsic::cttz, Zext, Op1);
+ return IC.replaceInstUsesWith(II, CttzZext);
+ }
+
// Zext doesn't change the number of trailing zeros, so narrow:
// cttz(zext(x)) -> zext(cttz(x)) if the 'ZeroIsUndef' parameter is 'true'.
if (match(Op0, m_OneUse(m_ZExt(m_Value(X)))) && match(Op1, m_One())) {
diff --git a/llvm/test/Transforms/InstCombine/cttz.ll b/llvm/test/Transforms/InstCombine/cttz.ll
index 8d50c68da37b..dd027de552cb 100644
--- a/llvm/test/Transforms/InstCombine/cttz.ll
+++ b/llvm/test/Transforms/InstCombine/cttz.ll
@@ -64,9 +64,9 @@ define <2 x i64> @cttz_zext_zero_def_vec(<2 x i32> %x) {
define i32 @cttz_sext_zero_undef(i16 %x) {
; CHECK-LABEL: @cttz_sext_zero_undef(
-; CHECK-NEXT: [[S:%.*]] = sext i16 [[X:%.*]] to i32
-; CHECK-NEXT: [[TZ:%.*]] = call i32 @llvm.cttz.i32(i32 [[S]], i1 true), !range [[RNG1]]
-; CHECK-NEXT: ret i32 [[TZ]]
+; CHECK-NEXT: [[TMP1:%.*]] = call i16 @llvm.cttz.i16(i16 [[X:%.*]], i1 true), !range [[RNG0]]
+; CHECK-NEXT: [[TMP2:%.*]] = zext i16 [[TMP1]] to i32
+; CHECK-NEXT: ret i32 [[TMP2]]
;
%s = sext i16 %x to i32
%tz = call i32 @llvm.cttz.i32(i32 %s, i1 true)
@@ -75,11 +75,11 @@ define i32 @cttz_sext_zero_undef(i16 %x) {
define i32 @cttz_sext_zero_def(i16 %x) {
; CHECK-LABEL: @cttz_sext_zero_def(
-; CHECK-NEXT: [[S:%.*]] = zext i16 [[X:%.*]] to i32
-; CHECK-NEXT: [[TZ:%.*]] = call i32 @llvm.cttz.i32(i32 [[S]], i1 false), !range [[RNG1]]
-; CHECK-NEXT: ret i32 [[TZ]]
+; CHECK-NEXT: [[TMP1:%.*]] = zext i16 [[X:%.*]] to i32
+; CHECK-NEXT: [[TMP2:%.*]] = call i32 @llvm.cttz.i32(i32 [[TMP1]], i1 false), !range [[RNG1]]
+; CHECK-NEXT: ret i32 [[TMP2]]
;
- %s = zext i16 %x to i32
+ %s = sext i16 %x to i32
%tz = call i32 @llvm.cttz.i32(i32 %s, i1 false)
ret i32 %tz
}
@@ -99,9 +99,9 @@ define i32 @cttz_sext_zero_undef_extra_use(i16 %x) {
define <2 x i64> @cttz_sext_zero_undef_vec(<2 x i32> %x) {
; CHECK-LABEL: @cttz_sext_zero_undef_vec(
-; CHECK-NEXT: [[S:%.*]] = sext <2 x i32> [[X:%.*]] to <2 x i64>
-; CHECK-NEXT: [[TZ:%.*]] = tail call <2 x i64> @llvm.cttz.v2i64(<2 x i64> [[S]], i1 true)
-; CHECK-NEXT: ret <2 x i64> [[TZ]]
+; CHECK-NEXT: [[TMP1:%.*]] = call <2 x i32> @llvm.cttz.v2i32(<2 x i32> [[X:%.*]], i1 true)
+; CHECK-NEXT: [[TMP2:%.*]] = zext <2 x i32> [[TMP1]] to <2 x i64>
+; CHECK-NEXT: ret <2 x i64> [[TMP2]]
;
%s = sext <2 x i32> %x to <2 x i64>
%tz = tail call <2 x i64> @llvm.cttz.v2i64(<2 x i64> %s, i1 true)
@@ -110,9 +110,9 @@ define <2 x i64> @cttz_sext_zero_undef_vec(<2 x i32> %x) {
define <2 x i64> @cttz_sext_zero_def_vec(<2 x i32> %x) {
; CHECK-LABEL: @cttz_sext_zero_def_vec(
-; CHECK-NEXT: [[S:%.*]] = sext <2 x i32> [[X:%.*]] to <2 x i64>
-; CHECK-NEXT: [[TZ:%.*]] = tail call <2 x i64> @llvm.cttz.v2i64(<2 x i64> [[S]], i1 false)
-; CHECK-NEXT: ret <2 x i64> [[TZ]]
+; CHECK-NEXT: [[TMP1:%.*]] = zext <2 x i32> [[X:%.*]] to <2 x i64>
+; CHECK-NEXT: [[TMP2:%.*]] = call <2 x i64> @llvm.cttz.v2i64(<2 x i64> [[TMP1]], i1 false)
+; CHECK-NEXT: ret <2 x i64> [[TMP2]]
;
%s = sext <2 x i32> %x to <2 x i64>
%tz = tail call <2 x i64> @llvm.cttz.v2i64(<2 x i64> %s, i1 false)
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