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

Summary:
For known positive non-zero value X:
    fcmp uge X, -C => true
    fcmp ugt X, -C => true
    fcmp une X, -C => true
    fcmp oeq X, -C => false
    fcmp ole X, -C => false
    fcmp olt X, -C => false


Patch by Paul Walker.

Reviewers: majnemer, t.p.northover, spatel, RKSimon

Reviewed By: spatel

Subscribers: fhahn, llvm-commits

Differential Revision: https://reviews.llvm.org/D40012

llvm-svn: 319538

lib/Analysis/InstructionSimplify.cpp

@@ -3378,6 +3378,28 @@ static Value *SimplifyFCmpInst(unsigned Predicate, Value *LHS, Value *RHS,
       default:
         break;
       }
+    } else if (C->isNegative()) {
+      assert(!C->isNaN() && "Unexpected NaN constant!");
+      // TODO: We can catch more cases by using a range check rather than
+      //       relying on CannotBeOrderedLessThanZero.
+      switch (Pred) {
+      case FCmpInst::FCMP_UGE:
+      case FCmpInst::FCMP_UGT:
+      case FCmpInst::FCMP_UNE:
+        // (X >= 0) implies (X > C) when (C < 0)
+        if (CannotBeOrderedLessThanZero(LHS, Q.TLI))
+          return getTrue(RetTy);
+        break;
+      case FCmpInst::FCMP_OEQ:
+      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;
+      }
     }
   }
 

test/Transforms/InstCombine/cast-int-fcmp-eq-0.ll

@@ -198,14 +198,6 @@ define i1 @i32_cast_cmp_ole_int_0_sitofp(i32 %i) {
   ret i1 %cmp
 }
 
-; CHECK-LABEL: @i32_cast_cmp_olt_int_0_uitofp(
-; CHECK: ret i1 false
-define i1 @i32_cast_cmp_olt_int_0_uitofp(i32 %i) {
-  %f = uitofp i32 %i to float
-  %cmp = fcmp olt float %f, 0.0
-  ret i1 %cmp
-}
-
 ; CHECK-LABEL: @i32_cast_cmp_olt_int_0_sitofp(
 ; CHECK: icmp slt i32 %i, 0
 ; CHECK-NEXT: ret
@@ -339,16 +331,6 @@ define i1 @i32_cast_cmp_oeq_int_i32umax_sitofp(i32 %i) {
   ret i1 %cmp
 }
 
-; CHECK-LABEL: @i32_cast_cmp_oeq_int_i32imin_uitofp(
-; CHECK: uitofp
-; CHECK: fcmp oeq
-; CHECK-NEXT: ret
-define i1 @i32_cast_cmp_oeq_int_i32imin_uitofp(i32 %i) {
-  %f = uitofp i32 %i to float
-  %cmp = fcmp oeq float %f, 0xC1E0000000000000
-  ret i1 %cmp
-}
-
 ; CHECK-LABEL: @i32_cast_cmp_oeq_int_i32imin_sitofp(
 ; CHECK: sitofp
 ; CHECK: fcmp oeq
@@ -379,16 +361,6 @@ define i1 @i32_cast_cmp_oeq_int_i32imax_sitofp(i32 %i) {
   ret i1 %cmp
 }
 
-; CHECK-LABEL: @i32_cast_cmp_oeq_int_negi32umax_uitofp(
-; CHECK: uitofp
-; CHECK: fcmp oeq
-; CHECK-NEXT: ret
-define i1 @i32_cast_cmp_oeq_int_negi32umax_uitofp(i32 %i) {
-  %f = uitofp i32 %i to float
-  %cmp = fcmp oeq float %f, 0xC1F0000000000000
-  ret i1 %cmp
-}
-
 ; 32-bit signed integer cannot possibly round to -1<<32
 ; CHECK-LABEL: @i32_cast_cmp_oeq_int_negi32umax_sitofp(
 ; CHECK-NEXT: ret i1 false

test/Transforms/InstSimplify/floating-point-compare.ll

@@ -169,8 +169,10 @@ define i1 @one_with_self(double %arg) {
 ; and between uge and olt, to give reasonble coverage
 ; without combinatorial explosion.
 
+declare half @llvm.fabs.f16(half)
 declare float @llvm.fabs.f32(float)
 declare double @llvm.fabs.f64(double)
+declare <2 x float> @llvm.fabs.v2f32(<2 x float>)
 declare <2 x double> @llvm.fabs.v2f64(<2 x double>)
 declare float @llvm.sqrt.f32(float)
 declare double @llvm.powi.f64(double,i32)
@@ -276,45 +278,55 @@ define i1 @orderedLessZeroMaxNum(float, float) {
 
 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:    ret i1 false
-; CHECK-NEXT:    [[CMP:%.*]] = fcmp olt double [[CALL]], -1.000000e+00
-; CHECK-NEXT:    ret i1 [[CMP]]
 ;
   %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) {
+define <2 x i1> @known_positive_ole_with_negative_constant_splat_vec(<2 x i32> %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:    ret <2 x i1> zeroinitializer
-; CHECK-NEXT:    [[CMP:%.*]] = fcmp ole <2 x double> [[CALL]], <double -2.000000e+00, double -2.000000e+00>
-; CHECK-NEXT:    ret <2 x i1> [[CMP]]
 ;
-  %call = call <2 x double> @llvm.fabs.v2f64(<2 x double> %a)
+  %call = uitofp <2 x i32> %a to <2 x double>
   %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) {
+define i1 @known_positive_ugt_with_negative_constant(i32 %a) {
 ; CHECK-LABEL: @known_positive_ugt_with_negative_constant(
-; CHECK-NEXT:    [[CALL:%.*]] = call double @llvm.fabs.f64(double %a)
+; CHECK-NEXT:    ret i1 true
-; CHECK-NEXT:    [[CMP:%.*]] = fcmp ugt double [[CALL]], -3.000000e+00
-; CHECK-NEXT:    ret i1 [[CMP]]
 ;
-  %call = call double @llvm.fabs.f64(double %a)
+  %call = uitofp i32 %a to float
-  %cmp = fcmp ugt double %call, -3.0
+  %cmp = fcmp ugt float %call, -3.0
   ret i1 %cmp
 }
 
-define <2 x i1> @known_positive_uge_with_negative_constant_splat_vec(<2 x double> %a) {
+define <2 x i1> @known_positive_uge_with_negative_constant_splat_vec(<2 x float> %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:    ret <2 x i1> <i1 true, i1 true>
-; CHECK-NEXT:    [[CMP:%.*]] = fcmp uge <2 x double> [[CALL]], <double -4.000000e+00, double -4.000000e+00>
-; CHECK-NEXT:    ret <2 x i1> [[CMP]]
 ;
-  %call = call <2 x double> @llvm.fabs.v2f64(<2 x double> %a)
+  %call = call <2 x float> @llvm.fabs.v2f32(<2 x float> %a)
-  %cmp = fcmp uge <2 x double> %call, <double -4.0, double -4.0>
+  %cmp = fcmp uge <2 x float> %call, <float -4.0, float -4.0>
+  ret <2 x i1> %cmp
+}
+
+define i1 @known_positive_oeq_with_negative_constant(half %a) {
+; CHECK-LABEL: @known_positive_oeq_with_negative_constant(
+; CHECK-NEXT:    ret i1 false
+;
+  %call = call half @llvm.fabs.f16(half %a)
+  %cmp = fcmp oeq half %call, -5.0
+  ret i1 %cmp
+}
+
+define <2 x i1> @known_positive_une_with_negative_constant_splat_vec(<2 x i32> %a) {
+; CHECK-LABEL: @known_positive_une_with_negative_constant_splat_vec(
+; CHECK-NEXT:    ret <2 x i1> <i1 true, i1 true>
+;
+  %call = uitofp <2 x i32> %a to <2 x half>
+  %cmp = fcmp une <2 x half> %call, <half -6.0, half -6.0>
   ret <2 x i1> %cmp
 }