[llvm] [ValueTracking] Infer relationship for the select with ICmp (PR #66668)

via llvm-commits llvm-commits at lists.llvm.org
Tue Dec 5 02:07:26 PST 2023


https://github.com/vfdff updated https://github.com/llvm/llvm-project/pull/66668

>From 52e4f8fbbcb530f8c1fa909c26d5eaebdf1ec283 Mon Sep 17 00:00:00 2001
From: zhongyunde 00443407 <zhongyunde at huawei.com>
Date: Mon, 18 Sep 2023 05:07:53 -0400
Subject: [PATCH 1/2] [tests] precommit tests for ValueTracking

x-y+1 is positive when x > y, so abs (x-y+1) --> x-y+1

Fixes https://github.com/llvm/llvm-project/issues/54735
---
 .../Transforms/InstSimplify/select-icmp.ll    | 256 ++++++++++++++++++
 1 file changed, 256 insertions(+)
 create mode 100755 llvm/test/Transforms/InstSimplify/select-icmp.ll

diff --git a/llvm/test/Transforms/InstSimplify/select-icmp.ll b/llvm/test/Transforms/InstSimplify/select-icmp.ll
new file mode 100755
index 0000000000000..482f9b8a8a9e8
--- /dev/null
+++ b/llvm/test/Transforms/InstSimplify/select-icmp.ll
@@ -0,0 +1,256 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -passes=instsimplify -S | FileCheck %s
+
+; TODO: https://alive2.llvm.org/ce/z/3ybZRl
+define i32 @pr54735_slt(i32 %x, i32 %y) {
+; CHECK-LABEL: @pr54735_slt(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[CMP:%.*]] = icmp slt i32 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    br i1 [[CMP]], label [[COND_TRUE:%.*]], label [[COND_END:%.*]]
+; CHECK:       cond.true:
+; CHECK-NEXT:    [[SUB:%.*]] = sub nsw i32 [[X]], [[Y]]
+; CHECK-NEXT:    [[ADD:%.*]] = add nsw i32 [[SUB]], 1
+; CHECK-NEXT:    [[NEG:%.*]] = xor i32 [[SUB]], -1
+; CHECK-NEXT:    [[ABSCOND:%.*]] = icmp sle i32 [[SUB]], -1
+; CHECK-NEXT:    [[ABS:%.*]] = select i1 [[ABSCOND]], i32 [[NEG]], i32 [[ADD]]
+; CHECK-NEXT:    ret i32 [[ABS]]
+; CHECK:       cond.end:
+; CHECK-NEXT:    ret i32 0
+;
+entry:
+  %cmp = icmp slt i32 %x, %y                      ; x<y ? abs (x-y+1): 0
+  br i1 %cmp, label %cond.true, label %cond.end
+
+cond.true:                                        ; preds = %entry
+  %sub = sub nsw i32 %x, %y
+  %add = add nsw i32 %sub, 1
+  %neg = xor i32 %sub, -1                         ; sub nsw i32 0, %add
+  %abscond = icmp sle i32 %sub, -1
+  %abs = select i1 %abscond, i32 %neg, i32 %add
+  ret i32 %abs
+
+cond.end:                                         ; preds = %entry, %cond.true
+  ret i32 0
+}
+
+; https://alive2.llvm.org/ce/z/fTTsdT
+define i32 @pr54735_sgt(i32 %x, i32 %y) {
+; CHECK-LABEL: @pr54735_sgt(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[CMP:%.*]] = icmp sgt i32 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    br i1 [[CMP]], label [[COND_TRUE:%.*]], label [[COND_END:%.*]]
+; CHECK:       cond.true:
+; CHECK-NEXT:    [[SUB:%.*]] = sub nsw i32 [[X]], [[Y]]
+; CHECK-NEXT:    [[ADD:%.*]] = add nsw i32 [[SUB]], 1
+; CHECK-NEXT:    [[NEG:%.*]] = xor i32 [[SUB]], -1
+; CHECK-NEXT:    [[ABSCOND:%.*]] = icmp slt i32 [[SUB]], -1
+; CHECK-NEXT:    [[ABS:%.*]] = select i1 [[ABSCOND]], i32 [[NEG]], i32 [[ADD]]
+; CHECK-NEXT:    ret i32 [[ABS]]
+; CHECK:       cond.end:
+; CHECK-NEXT:    ret i32 0
+;
+entry:
+  %cmp = icmp sgt i32 %x, %y                      ; x>y ? abs (x-y+1): 0
+  br i1 %cmp, label %cond.true, label %cond.end
+
+cond.true:                                        ; preds = %entry
+  %sub = sub nsw i32 %x, %y
+  %add = add nsw i32 %sub, 1
+  %neg = xor i32 %sub, -1                         ; sub nsw i32 0, %add
+  %abscond = icmp slt i32 %sub, -1
+  %abs = select i1 %abscond, i32 %neg, i32 %add
+  ret i32 %abs
+
+cond.end:                                         ; preds = %entry, %cond.true
+  ret i32 0
+}
+
+; https://alive2.llvm.org/ce/z/k9v75c
+define i32 @pr54735_sge(i32 %x, i32 %y) {
+; CHECK-LABEL: @pr54735_sge(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[CMP:%.*]] = icmp sge i32 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    br i1 [[CMP]], label [[COND_TRUE:%.*]], label [[COND_END:%.*]]
+; CHECK:       cond.true:
+; CHECK-NEXT:    [[SUB:%.*]] = sub nsw i32 [[X]], [[Y]]
+; CHECK-NEXT:    [[ADD:%.*]] = add nsw i32 [[SUB]], 1
+; CHECK-NEXT:    [[NEG:%.*]] = xor i32 [[SUB]], -1
+; CHECK-NEXT:    [[ABSCOND:%.*]] = icmp slt i32 [[SUB]], -1
+; CHECK-NEXT:    [[ABS:%.*]] = select i1 [[ABSCOND]], i32 [[NEG]], i32 [[ADD]]
+; CHECK-NEXT:    ret i32 [[ABS]]
+; CHECK:       cond.end:
+; CHECK-NEXT:    ret i32 0
+;
+entry:
+  %cmp = icmp sge i32 %x, %y                      ; x>y ? abs (x-y+1): 0
+  br i1 %cmp, label %cond.true, label %cond.end
+
+cond.true:                                        ; preds = %entry
+  %sub = sub nsw i32 %x, %y
+  %add = add nsw i32 %sub, 1
+  %neg = xor i32 %sub, -1                         ; sub nsw i32 0, %add
+  %abscond = icmp slt i32 %sub, -1
+  %abs = select i1 %abscond, i32 %neg, i32 %add
+  ret i32 %abs
+
+cond.end:                                         ; preds = %entry, %cond.true
+  ret i32 0
+}
+
+define i32 @pr54735_ugt(i32 %x, i32 %y) {
+; CHECK-LABEL: @pr54735_ugt(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ugt i32 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    br i1 [[CMP]], label [[COND_TRUE:%.*]], label [[COND_END:%.*]]
+; CHECK:       cond.true:
+; CHECK-NEXT:    [[SUB:%.*]] = sub nuw i32 [[X]], [[Y]]
+; CHECK-NEXT:    [[ADD:%.*]] = add nuw i32 [[SUB]], 2
+; CHECK-NEXT:    [[NEG:%.*]] = xor i32 [[SUB]], -2
+; CHECK-NEXT:    [[ABSCOND:%.*]] = icmp ult i32 [[SUB]], -2
+; CHECK-NEXT:    [[ABS:%.*]] = select i1 [[ABSCOND]], i32 [[NEG]], i32 [[ADD]]
+; CHECK-NEXT:    ret i32 [[ABS]]
+; CHECK:       cond.end:
+; CHECK-NEXT:    ret i32 0
+;
+entry:
+  %cmp = icmp ugt i32 %x, %y                      ; x>y ? abs (x-y+2): 0
+  br i1 %cmp, label %cond.true, label %cond.end
+
+cond.true:                                        ; preds = %entry
+  %sub = sub nuw i32 %x, %y
+  %add = add nuw i32 %sub, 2
+  %neg = xor i32 %sub, -2                         ; sub nuw i32 0, %add
+  %abscond = icmp ult i32 %sub, -2
+  %abs = select i1 %abscond, i32 %neg, i32 %add
+  ret i32 %abs
+
+cond.end:                                         ; preds = %entry, %cond.true
+  ret i32 0
+}
+
+define i32 @pr54735_uge(i32 %x, i32 %y) {
+; CHECK-LABEL: @pr54735_uge(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[CMP:%.*]] = icmp uge i32 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    br i1 [[CMP]], label [[COND_TRUE:%.*]], label [[COND_END:%.*]]
+; CHECK:       cond.true:
+; CHECK-NEXT:    [[SUB:%.*]] = sub nuw i32 [[X]], [[Y]]
+; CHECK-NEXT:    [[ADD:%.*]] = add nuw i32 [[SUB]], 2
+; CHECK-NEXT:    [[NEG:%.*]] = xor i32 [[SUB]], -2
+; CHECK-NEXT:    [[ABSCOND:%.*]] = icmp ult i32 [[SUB]], -2
+; CHECK-NEXT:    [[ABS:%.*]] = select i1 [[ABSCOND]], i32 [[NEG]], i32 [[ADD]]
+; CHECK-NEXT:    ret i32 [[ABS]]
+; CHECK:       cond.end:
+; CHECK-NEXT:    ret i32 0
+;
+entry:
+  %cmp = icmp uge i32 %x, %y                      ; x>y ? abs (x-y+2): 0
+  br i1 %cmp, label %cond.true, label %cond.end
+
+cond.true:                                        ; preds = %entry
+  %sub = sub nuw i32 %x, %y
+  %add = add nuw i32 %sub, 2
+  %neg = xor i32 %sub, -2                         ; sub nuw i32 0, %add
+  %abscond = icmp ult i32 %sub, -2
+  %abs = select i1 %abscond, i32 %neg, i32 %add
+  ret i32 %abs
+
+cond.end:                                         ; preds = %entry, %cond.true
+  ret i32 0
+}
+
+; Negative test: https://alive2.llvm.org/ce/z/oZyu4M
+define i8 @pr54735_without_nsw (i8 %x, i8 %y) {
+; CHECK-LABEL: @pr54735_without_nsw(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[CMP:%.*]] = icmp sgt i8 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    br i1 [[CMP]], label [[COND_TRUE:%.*]], label [[COND_END:%.*]]
+; CHECK:       cond.true:
+; CHECK-NEXT:    [[SUB:%.*]] = sub i8 [[X]], [[Y]]
+; CHECK-NEXT:    [[ADD:%.*]] = add i8 [[SUB]], 1
+; CHECK-NEXT:    [[NEG:%.*]] = xor i8 [[SUB]], -1
+; CHECK-NEXT:    [[ABSCOND:%.*]] = icmp slt i8 [[SUB]], -1
+; CHECK-NEXT:    [[ABS:%.*]] = select i1 [[ABSCOND]], i8 [[NEG]], i8 [[ADD]]
+; CHECK-NEXT:    ret i8 [[ABS]]
+; CHECK:       cond.end:
+; CHECK-NEXT:    ret i8 0
+;
+entry:
+  %cmp = icmp sgt i8 %x, %y
+  br i1 %cmp, label %cond.true, label %cond.end
+
+cond.true:                                        ; preds = %entry
+  %sub = sub i8 %x, %y
+  %add = add i8 %sub, 1
+  %neg = xor i8 %sub, -1
+  %abscond = icmp slt i8 %sub, -1
+  %abs = select i1 %abscond, i8 %neg, i8 %add
+  ret i8 %abs
+
+cond.end:                                         ; preds = %entry, %cond.true
+  ret i8 0
+}
+
+define i32 @pr54735_sle(i32 %x, i32 %y) {
+; CHECK-LABEL: @pr54735_sle(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[CMP:%.*]] = icmp sle i32 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    br i1 [[CMP]], label [[COND_TRUE:%.*]], label [[COND_END:%.*]]
+; CHECK:       cond.true:
+; CHECK-NEXT:    [[SUB:%.*]] = sub nsw i32 [[X]], [[Y]]
+; CHECK-NEXT:    [[ADD:%.*]] = add nsw i32 [[SUB]], 1
+; CHECK-NEXT:    [[NEG:%.*]] = xor i32 [[SUB]], -1
+; CHECK-NEXT:    [[ABSCOND:%.*]] = icmp slt i32 [[SUB]], -1
+; CHECK-NEXT:    [[ABS:%.*]] = select i1 [[ABSCOND]], i32 [[NEG]], i32 [[ADD]]
+; CHECK-NEXT:    ret i32 [[ABS]]
+; CHECK:       cond.end:
+; CHECK-NEXT:    ret i32 0
+;
+entry:
+  %cmp = icmp sle i32 %x, %y                      ; x<=y ? abs (x-y+1): 0
+  br i1 %cmp, label %cond.true, label %cond.end
+
+cond.true:                                        ; preds = %entry
+  %sub = sub nsw i32 %x, %y
+  %add = add nsw i32 %sub, 1
+  %neg = xor i32 %sub, -1                         ; sub nsw i32 0, %add
+  %abscond = icmp slt i32 %sub, -1
+  %abs = select i1 %abscond, i32 %neg, i32 %add
+  ret i32 %abs
+
+cond.end:                                         ; preds = %entry, %cond.true
+  ret i32 0
+}
+
+; Negative test: https://alive2.llvm.org/ce/z/Yqv4x2
+define i8 @pr54735_unexpect_const (i8 %x, i8 %y) {
+; CHECK-LABEL: @pr54735_unexpect_const(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[CMP:%.*]] = icmp sgt i8 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    br i1 [[CMP]], label [[COND_TRUE:%.*]], label [[COND_END:%.*]]
+; CHECK:       cond.true:
+; CHECK-NEXT:    [[SUB:%.*]] = sub i8 [[X]], [[Y]]
+; CHECK-NEXT:    [[ADD:%.*]] = add i8 [[SUB]], 2
+; CHECK-NEXT:    [[NEG:%.*]] = xor i8 [[SUB]], -1
+; CHECK-NEXT:    [[ABSCOND:%.*]] = icmp slt i8 [[SUB]], -2
+; CHECK-NEXT:    [[ABS:%.*]] = select i1 [[ABSCOND]], i8 [[NEG]], i8 [[ADD]]
+; CHECK-NEXT:    ret i8 [[ABS]]
+; CHECK:       cond.end:
+; CHECK-NEXT:    ret i8 0
+;
+entry:
+  %cmp = icmp sgt i8 %x, %y                       ; x>y ? abs (x-y+2): 0
+  br i1 %cmp, label %cond.true, label %cond.end
+
+cond.true:                                        ; preds = %entry
+  %sub = sub i8 %x, %y
+  %add = add i8 %sub, 2                           ; x-y+2
+  %neg = xor i8 %sub, -1                          ; y-x-1
+  %neg1 = sub i8 %neg, 1                          ; y-x-2
+  %abscond = icmp slt i8 %sub, -2
+  %abs = select i1 %abscond, i8 %neg, i8 %add
+  ret i8 %abs
+
+cond.end:                                         ; preds = %entry, %cond.true
+  ret i8 0
+}

>From 358cc404cc4f66b5b98d892532636e349e9bc2f9 Mon Sep 17 00:00:00 2001
From: zhongyunde 00443407 <zhongyunde at huawei.com>
Date: Mon, 18 Sep 2023 05:07:53 -0400
Subject: [PATCH 2/2] [ValueTracking] Infer relationship for the select with
 ICmp

x -nsw y < C is false when x > y and C <= 0
Alive2 proof for sgt, sge, ugt, uge : https://alive2.llvm.org/ce/z/tupvfi

Fixes https://github.com/llvm/llvm-project/issues/54735
---
 llvm/lib/Analysis/ValueTracking.cpp           | 13 ++++++++++++
 .../Transforms/InstSimplify/select-icmp.ll    | 20 ++++---------------
 2 files changed, 17 insertions(+), 16 deletions(-)

diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index 1f09d912f7339..df0aab7144213 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -8367,6 +8367,19 @@ static std::optional<bool> isImpliedCondICmps(const ICmpInst *LHS,
   if (areMatchingOperands(L0, L1, R0, R1, AreSwappedOps))
     return isImpliedCondMatchingOperands(LPred, RPred, AreSwappedOps);
 
+  // Take SGT as an example:  x > y and C <= 0 ==> x -nsw y < C is false
+  const APInt *CI;
+  Value *X, *Y;
+  if (((LPred == ICmpInst::ICMP_SGT || LPred == ICmpInst::ICMP_SGE) &&
+       match(R0, m_NSWSub(m_Value(X), m_Value(Y)))) ||
+      ((LPred == ICmpInst::ICMP_UGT || LPred == ICmpInst::ICMP_UGE) &&
+       match(R0, m_NUWSub(m_Value(X), m_Value(Y))))) {
+    if (match(R1, m_APInt(CI)) && CI->isNonPositive() &&
+        areMatchingOperands(L0, L1, X, Y, AreSwappedOps) &&
+        isImpliedCondMatchingOperands(LPred, RPred, AreSwappedOps) == false)
+      return false;
+  }
+
   // L0 = R0 = L1 + R1, L0 >=u L1 implies R0 >=u R1, L0 <u L1 implies R0 <u R1
   if (ICmpInst::isUnsigned(LPred) && ICmpInst::isUnsigned(RPred)) {
     if (L0 == R1) {
diff --git a/llvm/test/Transforms/InstSimplify/select-icmp.ll b/llvm/test/Transforms/InstSimplify/select-icmp.ll
index 482f9b8a8a9e8..23dfee8c60bd6 100755
--- a/llvm/test/Transforms/InstSimplify/select-icmp.ll
+++ b/llvm/test/Transforms/InstSimplify/select-icmp.ll
@@ -42,10 +42,7 @@ define i32 @pr54735_sgt(i32 %x, i32 %y) {
 ; CHECK:       cond.true:
 ; CHECK-NEXT:    [[SUB:%.*]] = sub nsw i32 [[X]], [[Y]]
 ; CHECK-NEXT:    [[ADD:%.*]] = add nsw i32 [[SUB]], 1
-; CHECK-NEXT:    [[NEG:%.*]] = xor i32 [[SUB]], -1
-; CHECK-NEXT:    [[ABSCOND:%.*]] = icmp slt i32 [[SUB]], -1
-; CHECK-NEXT:    [[ABS:%.*]] = select i1 [[ABSCOND]], i32 [[NEG]], i32 [[ADD]]
-; CHECK-NEXT:    ret i32 [[ABS]]
+; CHECK-NEXT:    ret i32 [[ADD]]
 ; CHECK:       cond.end:
 ; CHECK-NEXT:    ret i32 0
 ;
@@ -74,10 +71,7 @@ define i32 @pr54735_sge(i32 %x, i32 %y) {
 ; CHECK:       cond.true:
 ; CHECK-NEXT:    [[SUB:%.*]] = sub nsw i32 [[X]], [[Y]]
 ; CHECK-NEXT:    [[ADD:%.*]] = add nsw i32 [[SUB]], 1
-; CHECK-NEXT:    [[NEG:%.*]] = xor i32 [[SUB]], -1
-; CHECK-NEXT:    [[ABSCOND:%.*]] = icmp slt i32 [[SUB]], -1
-; CHECK-NEXT:    [[ABS:%.*]] = select i1 [[ABSCOND]], i32 [[NEG]], i32 [[ADD]]
-; CHECK-NEXT:    ret i32 [[ABS]]
+; CHECK-NEXT:    ret i32 [[ADD]]
 ; CHECK:       cond.end:
 ; CHECK-NEXT:    ret i32 0
 ;
@@ -105,10 +99,7 @@ define i32 @pr54735_ugt(i32 %x, i32 %y) {
 ; CHECK:       cond.true:
 ; CHECK-NEXT:    [[SUB:%.*]] = sub nuw i32 [[X]], [[Y]]
 ; CHECK-NEXT:    [[ADD:%.*]] = add nuw i32 [[SUB]], 2
-; CHECK-NEXT:    [[NEG:%.*]] = xor i32 [[SUB]], -2
-; CHECK-NEXT:    [[ABSCOND:%.*]] = icmp ult i32 [[SUB]], -2
-; CHECK-NEXT:    [[ABS:%.*]] = select i1 [[ABSCOND]], i32 [[NEG]], i32 [[ADD]]
-; CHECK-NEXT:    ret i32 [[ABS]]
+; CHECK-NEXT:    ret i32 [[ADD]]
 ; CHECK:       cond.end:
 ; CHECK-NEXT:    ret i32 0
 ;
@@ -136,10 +127,7 @@ define i32 @pr54735_uge(i32 %x, i32 %y) {
 ; CHECK:       cond.true:
 ; CHECK-NEXT:    [[SUB:%.*]] = sub nuw i32 [[X]], [[Y]]
 ; CHECK-NEXT:    [[ADD:%.*]] = add nuw i32 [[SUB]], 2
-; CHECK-NEXT:    [[NEG:%.*]] = xor i32 [[SUB]], -2
-; CHECK-NEXT:    [[ABSCOND:%.*]] = icmp ult i32 [[SUB]], -2
-; CHECK-NEXT:    [[ABS:%.*]] = select i1 [[ABSCOND]], i32 [[NEG]], i32 [[ADD]]
-; CHECK-NEXT:    ret i32 [[ABS]]
+; CHECK-NEXT:    ret i32 [[ADD]]
 ; CHECK:       cond.end:
 ; CHECK-NEXT:    ret i32 0
 ;



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