[llvm] [SCEV] Fix sext handling for `getConstantMultiple` (PR #117093)
Yingwei Zheng via llvm-commits
llvm-commits at lists.llvm.org
Wed Nov 20 17:40:48 PST 2024
https://github.com/dtcxzyw created https://github.com/llvm/llvm-project/pull/117093
Counterexample: 219 is a multiple of 73. But `sext i8 219 to i16 = 65499` is not.
Fixes https://github.com/llvm/llvm-project/issues/116483.
>From 3ddfe7ac7e6f8bb7aa812bd2a6ce962796a42810 Mon Sep 17 00:00:00 2001
From: Yingwei Zheng <dtcxzyw2333 at gmail.com>
Date: Thu, 21 Nov 2024 09:07:56 +0800
Subject: [PATCH 1/2] [SCEV] Add pre-commit tests. NFC.
---
.../test/Analysis/ScalarEvolution/pr116483.ll | 26 ++++++++++++++
.../Transforms/IndVarSimplify/pr116483.ll | 36 +++++++++++++++++++
2 files changed, 62 insertions(+)
create mode 100644 llvm/test/Analysis/ScalarEvolution/pr116483.ll
create mode 100644 llvm/test/Transforms/IndVarSimplify/pr116483.ll
diff --git a/llvm/test/Analysis/ScalarEvolution/pr116483.ll b/llvm/test/Analysis/ScalarEvolution/pr116483.ll
new file mode 100644
index 00000000000000..a58badc0e20904
--- /dev/null
+++ b/llvm/test/Analysis/ScalarEvolution/pr116483.ll
@@ -0,0 +1,26 @@
+; NOTE: Assertions have been autogenerated by utils/update_analyze_test_checks.py UTC_ARGS: --version 5
+; RUN: opt -S -disable-output "-passes=print<scalar-evolution>" < %s 2>&1 | FileCheck %s
+
+define i16 @test() {
+; CHECK-LABEL: 'test'
+; CHECK-NEXT: Classifying expressions for: @test
+; CHECK-NEXT: %xor = xor i32 0, 3
+; CHECK-NEXT: --> %xor U: [3,4) S: [3,4)
+; CHECK-NEXT: %mul = mul i32 %xor, 329
+; CHECK-NEXT: --> (329 * %xor)<nuw><nsw> U: [987,988) S: [987,988)
+; CHECK-NEXT: %conv = trunc i32 %mul to i16
+; CHECK-NEXT: --> (329 * (trunc i32 %xor to i16))<nuw><nsw> U: [987,988) S: [987,988)
+; CHECK-NEXT: %sext = shl i16 %conv, 8
+; CHECK-NEXT: --> (18688 * (trunc i32 %xor to i16))<nuw> U: [-9472,-9471) S: [-9472,-9471)
+; CHECK-NEXT: %conv1 = ashr i16 %sext, 8
+; CHECK-NEXT: --> (sext i8 (73 * (trunc i32 %xor to i8))<nuw> to i16) U: empty-set S: [-37,-36)
+; CHECK-NEXT: Determining loop execution counts for: @test
+;
+entry:
+ %xor = xor i32 0, 3
+ %mul = mul i32 %xor, 329
+ %conv = trunc i32 %mul to i16
+ %sext = shl i16 %conv, 8
+ %conv1 = ashr i16 %sext, 8
+ ret i16 %conv1
+}
diff --git a/llvm/test/Transforms/IndVarSimplify/pr116483.ll b/llvm/test/Transforms/IndVarSimplify/pr116483.ll
new file mode 100644
index 00000000000000..a57e6d563eb028
--- /dev/null
+++ b/llvm/test/Transforms/IndVarSimplify/pr116483.ll
@@ -0,0 +1,36 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt -S -passes=indvars < %s | FileCheck %s
+
+define i32 @test() {
+; CHECK-LABEL: define i32 @test() {
+; CHECK-NEXT: [[ENTRY:.*:]]
+; CHECK-NEXT: [[XOR:%.*]] = xor i32 0, 3
+; CHECK-NEXT: [[MUL:%.*]] = mul i32 [[XOR]], 329
+; CHECK-NEXT: [[CONV:%.*]] = trunc i32 [[MUL]] to i16
+; CHECK-NEXT: [[SEXT:%.*]] = shl i16 [[CONV]], 8
+; CHECK-NEXT: [[CONV1:%.*]] = ashr i16 [[SEXT]], 8
+; CHECK-NEXT: br label %[[LOOP_BODY:.*]]
+; CHECK: [[LOOP_BODY]]:
+; CHECK-NEXT: br i1 false, label %[[EXIT:.*]], label %[[LOOP_BODY]]
+; CHECK: [[EXIT]]:
+; CHECK-NEXT: [[CONV3:%.*]] = zext i16 [[CONV1]] to i32
+; CHECK-NEXT: ret i32 [[CONV3]]
+;
+entry:
+ %xor = xor i32 0, 3
+ %mul = mul i32 %xor, 329
+ %conv = trunc i32 %mul to i16
+ %sext = shl i16 %conv, 8
+ %conv1 = ashr i16 %sext, 8
+ %conv3 = zext i16 %conv1 to i32
+ br label %loop.body
+
+loop.body:
+ %indvar = phi i32 [ %indvar.inc, %loop.body ], [ 1, %entry ]
+ %indvar.inc = add nuw i32 %indvar, 1
+ %exitcond = icmp eq i32 %indvar, %conv3
+ br i1 %exitcond, label %exit, label %loop.body
+
+exit:
+ ret i32 %conv3
+}
>From 50f03d7a5174466291d0aa23f9d9434e1aa8aede Mon Sep 17 00:00:00 2001
From: Yingwei Zheng <dtcxzyw2333 at gmail.com>
Date: Thu, 21 Nov 2024 09:36:01 +0800
Subject: [PATCH 2/2] [SCEV] Fix sext handling for `getConstantMultiple`
---
llvm/lib/Analysis/ScalarEvolution.cpp | 4 +++-
llvm/test/Analysis/ScalarEvolution/pr116483.ll | 2 +-
llvm/test/Transforms/IndVarSimplify/pr116483.ll | 2 +-
3 files changed, 5 insertions(+), 3 deletions(-)
diff --git a/llvm/lib/Analysis/ScalarEvolution.cpp b/llvm/lib/Analysis/ScalarEvolution.cpp
index 46b108606f6a62..0ff4e0f74fb675 100644
--- a/llvm/lib/Analysis/ScalarEvolution.cpp
+++ b/llvm/lib/Analysis/ScalarEvolution.cpp
@@ -6314,8 +6314,10 @@ APInt ScalarEvolution::getConstantMultipleImpl(const SCEV *S) {
return getConstantMultiple(Z->getOperand()).zext(BitWidth);
}
case scSignExtend: {
+ // Only multiples that are a power of 2 will hold after sext.
const SCEVSignExtendExpr *E = cast<SCEVSignExtendExpr>(S);
- return getConstantMultiple(E->getOperand()).sext(BitWidth);
+ uint32_t TZ = getMinTrailingZeros(E->getOperand());
+ return GetShiftedByZeros(TZ);
}
case scMulExpr: {
const SCEVMulExpr *M = cast<SCEVMulExpr>(S);
diff --git a/llvm/test/Analysis/ScalarEvolution/pr116483.ll b/llvm/test/Analysis/ScalarEvolution/pr116483.ll
index a58badc0e20904..cc2334e9c64f92 100644
--- a/llvm/test/Analysis/ScalarEvolution/pr116483.ll
+++ b/llvm/test/Analysis/ScalarEvolution/pr116483.ll
@@ -13,7 +13,7 @@ define i16 @test() {
; CHECK-NEXT: %sext = shl i16 %conv, 8
; CHECK-NEXT: --> (18688 * (trunc i32 %xor to i16))<nuw> U: [-9472,-9471) S: [-9472,-9471)
; CHECK-NEXT: %conv1 = ashr i16 %sext, 8
-; CHECK-NEXT: --> (sext i8 (73 * (trunc i32 %xor to i8))<nuw> to i16) U: empty-set S: [-37,-36)
+; CHECK-NEXT: --> (sext i8 (73 * (trunc i32 %xor to i8))<nuw> to i16) U: [-37,-36) S: [-37,-36)
; CHECK-NEXT: Determining loop execution counts for: @test
;
entry:
diff --git a/llvm/test/Transforms/IndVarSimplify/pr116483.ll b/llvm/test/Transforms/IndVarSimplify/pr116483.ll
index a57e6d563eb028..ae108a525223e0 100644
--- a/llvm/test/Transforms/IndVarSimplify/pr116483.ll
+++ b/llvm/test/Transforms/IndVarSimplify/pr116483.ll
@@ -11,7 +11,7 @@ define i32 @test() {
; CHECK-NEXT: [[CONV1:%.*]] = ashr i16 [[SEXT]], 8
; CHECK-NEXT: br label %[[LOOP_BODY:.*]]
; CHECK: [[LOOP_BODY]]:
-; CHECK-NEXT: br i1 false, label %[[EXIT:.*]], label %[[LOOP_BODY]]
+; CHECK-NEXT: br i1 true, label %[[EXIT:.*]], label %[[LOOP_BODY]]
; CHECK: [[EXIT]]:
; CHECK-NEXT: [[CONV3:%.*]] = zext i16 [[CONV1]] to i32
; CHECK-NEXT: ret i32 [[CONV3]]
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