[PATCH] D128790: [InstCombine] improve fold for icmp_eq_and to icmp_ult

[Chenbing.Zheng via Phabricator via llvm-commits]

This revision was landed with ongoing or failed builds.
This revision was automatically updated to reflect the committed changes.
Closed by commit rGb43dd2f6c4a3: [InstCombine] improve fold for icmp_eq_and to icmp_ult (authored by Chenbing.Zheng).

Changed prior to commit:
  https://reviews.llvm.org/D128790?vs=442014&id=442229#toc

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D128790/new/

https://reviews.llvm.org/D128790

Files:
  llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
  llvm/test/Transforms/InstCombine/lshr-and-negC-icmpeq-zero.ll


Index: llvm/test/Transforms/InstCombine/lshr-and-negC-icmpeq-zero.ll
===================================================================
--- llvm/test/Transforms/InstCombine/lshr-and-negC-icmpeq-zero.ll
+++ llvm/test/Transforms/InstCombine/lshr-and-negC-icmpeq-zero.ll
@@ -177,15 +177,10 @@
   ret i1 %r
 }
 
-; Negative tests
-
-; TODO: This could be reduced to lshr+icmp ult.
-
 define i1 @scalar_i32_lshr_and_negC_eq_X_is_constant1(i32 %y) {
 ; CHECK-LABEL: @scalar_i32_lshr_and_negC_eq_X_is_constant1(
 ; CHECK-NEXT:    [[LSHR:%.*]] = lshr i32 12345, [[Y:%.*]]
-; CHECK-NEXT:    [[AND:%.*]] = and i32 [[LSHR]], 16376
-; CHECK-NEXT:    [[R:%.*]] = icmp eq i32 [[AND]], 0
+; CHECK-NEXT:    [[R:%.*]] = icmp ult i32 [[LSHR]], 8
 ; CHECK-NEXT:    ret i1 [[R]]
 ;
   %lshr = lshr i32 12345, %y
@@ -194,13 +189,9 @@
   ret i1 %r
 }
 
-; TODO: This could be reduced to lshr+icmp ult.
-
 define i1 @scalar_i32_lshr_and_negC_eq_X_is_constant2(i32 %y) {
 ; CHECK-LABEL: @scalar_i32_lshr_and_negC_eq_X_is_constant2(
-; CHECK-NEXT:    [[LSHR:%.*]] = lshr i32 268435456, [[Y:%.*]]
-; CHECK-NEXT:    [[AND:%.*]] = and i32 [[LSHR]], 536870904
-; CHECK-NEXT:    [[R:%.*]] = icmp eq i32 [[AND]], 0
+; CHECK-NEXT:    [[R:%.*]] = icmp ugt i32 [[Y:%.*]], 25
 ; CHECK-NEXT:    ret i1 [[R]]
 ;
   %lshr = lshr i32 268435456, %y
@@ -208,7 +199,31 @@
   %r = icmp eq i32 %and, 0
   ret i1 %r
 }
+define i1 @scalar_i32_udiv_and_negC_eq_X_is_constant3(i32 %y) {
+; CHECK-LABEL: @scalar_i32_udiv_and_negC_eq_X_is_constant3(
+; CHECK-NEXT:    [[R:%.*]] = icmp ult i32 [[Y:%.*]], 1544
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %lshr = udiv  i32 12345, %y
+  %and = and i32 %lshr, 16376    ; 0x3ff8
+  %r = icmp ne i32 %and, 0
+  ret i1 %r
+}
+
+; Negative test
 
+define i1 @scalar_i32_lshr_and_negC_eq_X_is_constant_negtive(i32 %y) {
+; CHECK-LABEL: @scalar_i32_lshr_and_negC_eq_X_is_constant_negtive(
+; CHECK-NEXT:    [[LSHR:%.*]] = lshr i32 16384, [[Y:%.*]]
+; CHECK-NEXT:    [[AND:%.*]] = and i32 [[LSHR]], 16376
+; CHECK-NEXT:    [[R:%.*]] = icmp eq i32 [[AND]], 0
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %lshr = lshr i32 16384, %y    ; 0x4000
+  %and = and i32 %lshr, 16376   ; 0x3ff8
+  %r = icmp eq i32 %and, 0
+  ret i1 %r
+}
 ; Check 'slt' predicate
 
 define i1 @scalar_i32_lshr_and_negC_slt(i32 %x, i32 %y) {
Index: llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -1777,11 +1777,16 @@
       return new ICmpInst(NewPred, X, Zero);
     }
 
+    APInt NewC2 = *C2;
+    KnownBits Know = computeKnownBits(And->getOperand(0), 0, And);
+    // Set high zeros of C2 to allow matching negated power-of-2.
+    NewC2 = *C2 + APInt::getHighBitsSet(C2->getBitWidth(),
+                                        Know.countMinLeadingZeros());
+
     // Restrict this fold only for single-use 'and' (PR10267).
     // ((%x & C) == 0) --> %x u< (-C)  iff (-C) is power of two.
-    if (C2->isNegatedPowerOf2()) {
-      Constant *NegBOC =
-          ConstantExpr::getNeg(cast<Constant>(And->getOperand(1)));
+    if (NewC2.isNegatedPowerOf2()) {
+      Constant *NegBOC = ConstantInt::get(And->getType(), -NewC2);
       auto NewPred = isICMP_NE ? ICmpInst::ICMP_UGE : ICmpInst::ICMP_ULT;
       return new ICmpInst(NewPred, X, NegBOC);
     }


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