[llvm] 9facaad - [ValueTracking] Improve tracking for constant range of `{s|u}rem C, x`

[Noah Goldstein via llvm-commits]

Author: Noah Goldstein
Date: 2024-02-20T10:39:34-06:00
New Revision: 9facaaddadd63a1668c212c8a9ef94a5ad4c6629

URL: https://github.com/llvm/llvm-project/commit/9facaaddadd63a1668c212c8a9ef94a5ad4c6629
DIFF: https://github.com/llvm/llvm-project/commit/9facaaddadd63a1668c212c8a9ef94a5ad4c6629.diff

LOG: [ValueTracking] Improve tracking for constant range of `{s|u}rem C, x`

Current we only support `C` as the remainder, but we can also limit
with a constant numerator.

Proofs: https://alive2.llvm.org/ce/z/QB95gU

Closes #82303

Added: 
    

Modified: 
    llvm/lib/Analysis/ValueTracking.cpp
    llvm/test/Analysis/ValueTracking/constant-ranges.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index 1a076adb1bad0a..04f317228b3ea7 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -8776,6 +8776,15 @@ static void setLimitsForBinOp(const BinaryOperator &BO, APInt &Lower,
       // 'srem x, C' produces (-|C|, |C|).
       Upper = C->abs();
       Lower = (-Upper) + 1;
+    } else if (match(BO.getOperand(0), m_APInt(C))) {
+      if (C->isNegative()) {
+        // 'srem -|C|, x' produces [-|C|, 0].
+        Upper = 1;
+        Lower = *C;
+      } else {
+        // 'srem |C|, x' produces [0, |C|].
+        Upper = *C + 1;
+      }
     }
     break;
 
@@ -8783,6 +8792,9 @@ static void setLimitsForBinOp(const BinaryOperator &BO, APInt &Lower,
     if (match(BO.getOperand(1), m_APInt(C)))
       // 'urem x, C' produces [0, C).
       Upper = *C;
+    else if (match(BO.getOperand(0), m_APInt(C)))
+      // 'urem C, x' produces [0, C].
+      Upper = *C + 1;
     break;
 
   default:

diff  --git a/llvm/test/Analysis/ValueTracking/constant-ranges.ll b/llvm/test/Analysis/ValueTracking/constant-ranges.ll
index addfe0fc4c54d6..c440cfad889d3b 100644
--- a/llvm/test/Analysis/ValueTracking/constant-ranges.ll
+++ b/llvm/test/Analysis/ValueTracking/constant-ranges.ll
@@ -133,9 +133,7 @@ define i1 @and_ugt_fail(i8 %xx) {
 
 define i1 @urem_okay(i8 %x) {
 ; CHECK-LABEL: @urem_okay(
-; CHECK-NEXT:    [[VAL:%.*]] = urem i8 34, [[X:%.*]]
-; CHECK-NEXT:    [[R:%.*]] = icmp ule i8 [[VAL]], 35
-; CHECK-NEXT:    ret i1 [[R]]
+; CHECK-NEXT:    ret i1 true
 ;
   %val = urem i8 34, %x
   %r = icmp ule i8 %val, 35
@@ -155,9 +153,7 @@ define i1 @urem_fail(i8 %x) {
 
 define i1 @srem_posC_okay0(i8 %x) {
 ; CHECK-LABEL: @srem_posC_okay0(
-; CHECK-NEXT:    [[VAL:%.*]] = srem i8 34, [[X:%.*]]
-; CHECK-NEXT:    [[R:%.*]] = icmp sle i8 [[VAL]], 34
-; CHECK-NEXT:    ret i1 [[R]]
+; CHECK-NEXT:    ret i1 true
 ;
   %val = srem i8 34, %x
   %r = icmp sle i8 %val, 34
@@ -166,9 +162,7 @@ define i1 @srem_posC_okay0(i8 %x) {
 
 define i1 @srem_posC_okay1(i8 %x) {
 ; CHECK-LABEL: @srem_posC_okay1(
-; CHECK-NEXT:    [[VAL:%.*]] = srem i8 34, [[X:%.*]]
-; CHECK-NEXT:    [[R:%.*]] = icmp sge i8 [[VAL]], -3
-; CHECK-NEXT:    ret i1 [[R]]
+; CHECK-NEXT:    ret i1 true
 ;
   %val = srem i8 34, %x
   %r = icmp sge i8 %val, -3
@@ -177,9 +171,7 @@ define i1 @srem_posC_okay1(i8 %x) {
 
 define i1 @srem_negC_okay0(i8 %x) {
 ; CHECK-LABEL: @srem_negC_okay0(
-; CHECK-NEXT:    [[VAL:%.*]] = srem i8 -34, [[X:%.*]]
-; CHECK-NEXT:    [[R:%.*]] = icmp sle i8 [[VAL]], 0
-; CHECK-NEXT:    ret i1 [[R]]
+; CHECK-NEXT:    ret i1 true
 ;
   %val = srem i8 -34, %x
   %r = icmp sle i8 %val, 0
@@ -188,9 +180,7 @@ define i1 @srem_negC_okay0(i8 %x) {
 
 define i1 @srem_negC_okay1(i8 %x) {
 ; CHECK-LABEL: @srem_negC_okay1(
-; CHECK-NEXT:    [[VAL:%.*]] = srem i8 -34, [[X:%.*]]
-; CHECK-NEXT:    [[R:%.*]] = icmp sge i8 [[VAL]], -34
-; CHECK-NEXT:    ret i1 [[R]]
+; CHECK-NEXT:    ret i1 true
 ;
   %val = srem i8 -34, %x
   %r = icmp sge i8 %val, -34