[PATCH] D40012: [InstSimplify] More fcmp cases when comparing against negative constants.

[Paul Walker via Phabricator via llvm-commits]

paulwalker-arm updated this revision to Diff 124589.
paulwalker-arm edited the summary of this revision.
paulwalker-arm added a comment.

Broke out the isNegative case into its own block so that more conditions can be handled when it's known the constant is non-zero.  Removed my original tests and updated the existing ones to reflect the optimised output.


https://reviews.llvm.org/D40012

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


Index: test/Transforms/InstSimplify/floating-point-compare.ll
===================================================================
--- test/Transforms/InstSimplify/floating-point-compare.ll
+++ test/Transforms/InstSimplify/floating-point-compare.ll
@@ -276,42 +276,34 @@
 
 define i1 @known_positive_olt_with_negative_constant(double %a) {
 ; CHECK-LABEL: @known_positive_olt_with_negative_constant(
-; CHECK-NEXT:    [[CALL:%.*]] = call double @llvm.fabs.f64(double %a)
-; CHECK-NEXT:    [[CMP:%.*]] = fcmp olt double [[CALL]], -1.000000e+00
-; CHECK-NEXT:    ret i1 [[CMP]]
+; CHECK-NEXT:    ret i1 false
 ;
   %call = call double @llvm.fabs.f64(double %a)
   %cmp = fcmp olt double %call, -1.0
   ret i1 %cmp
 }
 
 define <2 x i1> @known_positive_ole_with_negative_constant_splat_vec(<2 x double> %a) {
 ; CHECK-LABEL: @known_positive_ole_with_negative_constant_splat_vec(
-; CHECK-NEXT:    [[CALL:%.*]] = call <2 x double> @llvm.fabs.v2f64(<2 x double> %a)
-; CHECK-NEXT:    [[CMP:%.*]] = fcmp ole <2 x double> [[CALL]], <double -2.000000e+00, double -2.000000e+00>
-; CHECK-NEXT:    ret <2 x i1> [[CMP]]
+; CHECK-NEXT:    ret <2 x i1> zeroinitializer
 ;
   %call = call <2 x double> @llvm.fabs.v2f64(<2 x double> %a)
   %cmp = fcmp ole <2 x double> %call, <double -2.0, double -2.0>
   ret <2 x i1> %cmp
 }
 
 define i1 @known_positive_ugt_with_negative_constant(double %a) {
 ; CHECK-LABEL: @known_positive_ugt_with_negative_constant(
-; CHECK-NEXT:    [[CALL:%.*]] = call double @llvm.fabs.f64(double %a)
-; CHECK-NEXT:    [[CMP:%.*]] = fcmp ugt double [[CALL]], -3.000000e+00
-; CHECK-NEXT:    ret i1 [[CMP]]
+; CHECK-NEXT:    ret i1 true
 ;
   %call = call double @llvm.fabs.f64(double %a)
   %cmp = fcmp ugt double %call, -3.0
   ret i1 %cmp
 }
 
 define <2 x i1> @known_positive_uge_with_negative_constant_splat_vec(<2 x double> %a) {
 ; CHECK-LABEL: @known_positive_uge_with_negative_constant_splat_vec(
-; CHECK-NEXT:    [[CALL:%.*]] = call <2 x double> @llvm.fabs.v2f64(<2 x double> %a)
-; CHECK-NEXT:    [[CMP:%.*]] = fcmp uge <2 x double> [[CALL]], <double -4.000000e+00, double -4.000000e+00>
-; CHECK-NEXT:    ret <2 x i1> [[CMP]]
+; CHECK-NEXT:    ret <2 x i1> <i1 true, i1 true>
 ;
   %call = call <2 x double> @llvm.fabs.v2f64(<2 x double> %a)
   %cmp = fcmp uge <2 x double> %call, <double -4.0, double -4.0>
Index: lib/Analysis/InstructionSimplify.cpp
===================================================================
--- lib/Analysis/InstructionSimplify.cpp
+++ lib/Analysis/InstructionSimplify.cpp
@@ -3378,6 +3378,23 @@
       default:
         break;
       }
+    } else if (C->isNegative()) {
+      switch (Pred) {
+      case FCmpInst::FCMP_UGE:
+      case FCmpInst::FCMP_UGT:
+        // (X >= 0) implies (X > C) when (C < 0)
+        if (CannotBeOrderedLessThanZero(LHS, Q.TLI))
+          return getTrue(RetTy);
+        break;
+      case FCmpInst::FCMP_OLE:
+      case FCmpInst::FCMP_OLT:
+        // (X >= 0) implies !(X < C) when (C < 0)
+        if (CannotBeOrderedLessThanZero(LHS, Q.TLI))
+          return getFalse(RetTy);
+        break;
+      default:
+        break;
+      }
     }
   }
 


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D40012.124589.patch
Type: text/x-patch
Size: 3139 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20171128/e961f79f/attachment.bin>