[PATCH] D139319: ValueTracking: Teach isKnownNeverInfinity about llvm.log*

[Matt Arsenault via Phabricator via llvm-commits]

arsenm created this revision.
arsenm added reviewers: spatel, nlopes, jcranmer-intel, sepavloff, kpn, andrew.w.kaylor.
Herald added a subscriber: hiraditya.
Herald added a project: All.
arsenm requested review of this revision.
Herald added a subscriber: wdng.
Herald added a project: LLVM.

https://reviews.llvm.org/D139319

Files:
  llvm/lib/Analysis/ValueTracking.cpp
  llvm/test/Transforms/InstSimplify/floating-point-compare.ll


Index: llvm/test/Transforms/InstSimplify/floating-point-compare.ll
===================================================================
--- llvm/test/Transforms/InstSimplify/floating-point-compare.ll
+++ llvm/test/Transforms/InstSimplify/floating-point-compare.ll
@@ -1752,11 +1752,7 @@
 
 define i1 @isKnownNeverInfinity_log(double %x) {
 ; CHECK-LABEL: @isKnownNeverInfinity_log(
-; CHECK-NEXT:    [[X_CLAMP_ZERO:%.*]] = call double @llvm.maxnum.f64(double [[X:%.*]], double 0.000000e+00)
-; CHECK-NEXT:    [[A:%.*]] = fadd ninf double [[X_CLAMP_ZERO]], 1.000000e+00
-; CHECK-NEXT:    [[E:%.*]] = call double @llvm.log.f64(double [[A]])
-; CHECK-NEXT:    [[R:%.*]] = fcmp une double [[E]], 0x7FF0000000000000
-; CHECK-NEXT:    ret i1 [[R]]
+; CHECK-NEXT:    ret i1 true
 ;
   %x.clamp.zero = call double @llvm.maxnum.f64(double %x, double 0.0)
   %a = fadd ninf double %x.clamp.zero, 1.0
@@ -1796,11 +1792,7 @@
 
 define i1 @isKnownNeverInfinity_log10(double %x) {
 ; CHECK-LABEL: @isKnownNeverInfinity_log10(
-; CHECK-NEXT:    [[X_CLAMP_ZERO:%.*]] = call double @llvm.maxnum.f64(double [[X:%.*]], double 0.000000e+00)
-; CHECK-NEXT:    [[A:%.*]] = fadd ninf double [[X_CLAMP_ZERO]], 1.000000e+00
-; CHECK-NEXT:    [[E:%.*]] = call double @llvm.log10.f64(double [[A]])
-; CHECK-NEXT:    [[R:%.*]] = fcmp une double [[E]], 0x7FF0000000000000
-; CHECK-NEXT:    ret i1 [[R]]
+; CHECK-NEXT:    ret i1 true
 ;
   %x.clamp.zero = call double @llvm.maxnum.f64(double %x, double 0.0)
   %a = fadd ninf double %x.clamp.zero, 1.0
@@ -1840,11 +1832,7 @@
 
 define i1 @isKnownNeverInfinity_log2(double %x) {
 ; CHECK-LABEL: @isKnownNeverInfinity_log2(
-; CHECK-NEXT:    [[X_CLAMP_ZERO:%.*]] = call double @llvm.maxnum.f64(double [[X:%.*]], double 0.000000e+00)
-; CHECK-NEXT:    [[A:%.*]] = fadd ninf double [[X_CLAMP_ZERO]], 1.000000e+00
-; CHECK-NEXT:    [[E:%.*]] = call double @llvm.log2.f64(double [[A]])
-; CHECK-NEXT:    [[R:%.*]] = fcmp une double [[E]], 0x7FF0000000000000
-; CHECK-NEXT:    ret i1 [[R]]
+; CHECK-NEXT:    ret i1 true
 ;
   %x.clamp.zero = call double @llvm.maxnum.f64(double %x, double 0.0)
   %a = fadd ninf double %x.clamp.zero, 1.0
Index: llvm/lib/Analysis/ValueTracking.cpp
===================================================================
--- llvm/lib/Analysis/ValueTracking.cpp
+++ llvm/lib/Analysis/ValueTracking.cpp
@@ -3833,6 +3833,16 @@
       case Intrinsic::maximum:
       return isKnownNeverInfinity(Inst->getOperand(0), TLI, Depth + 1) &&
              isKnownNeverInfinity(Inst->getOperand(1), TLI, Depth + 1);
+      case Intrinsic::log:
+      case Intrinsic::log10:
+      case Intrinsic::log2:
+      // log(+inf) -> +inf
+      // log([+-]0.0) -> -inf
+      // log(-inf) -> nan
+      // log(-x) -> nan
+      return isKnownNeverInfinity(Inst->getOperand(0), TLI, Depth + 1) &&
+             cannotBeOrderedLessThanZeroImpl(Inst->getOperand(0), TLI,
+                                             /*SignBitOnly=*/false, Depth + 1);
       default:
         break;
       }


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