From: Dan Gohman <gohman@apple.com>
Date: Mon, 22 Feb 2010 04:06:03 +0000 (+0000)
Subject: Constant-fold certain comparisons with infinity and negative infinity.
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=6b617a7213e159097a7e5c7216ed9b04921de4e1;p=oota-llvm.git

Constant-fold certain comparisons with infinity and negative infinity.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@96777 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Analysis/InstructionSimplify.cpp b/lib/Analysis/InstructionSimplify.cpp
index b53ac13925b..1f8053afe94 100644
--- a/lib/Analysis/InstructionSimplify.cpp
+++ b/lib/Analysis/InstructionSimplify.cpp
@@ -283,6 +283,32 @@ Value *llvm::SimplifyFCmpInst(unsigned Predicate, Value *LHS, Value *RHS,
         // True if unordered.
         return ConstantInt::getTrue(CFP->getContext());
       }
+      // Check whether the constant is an infinity.
+      if (CFP->getValueAPF().isInfinity()) {
+        if (CFP->getValueAPF().isNegative()) {
+          switch (Pred) {
+          case FCmpInst::FCMP_OLT:
+            // No value is ordered and less than negative infinity.
+            return ConstantInt::getFalse(CFP->getContext());
+          case FCmpInst::FCMP_UGE:
+            // All values are unordered with or at least negative infinity.
+            return ConstantInt::getTrue(CFP->getContext());
+          default:
+            break;
+          }
+        } else {
+          switch (Pred) {
+          case FCmpInst::FCMP_OGT:
+            // No value is ordered and greater than infinity.
+            return ConstantInt::getFalse(CFP->getContext());
+          case FCmpInst::FCMP_ULE:
+            // All values are unordered with and at most infinity.
+            return ConstantInt::getTrue(CFP->getContext());
+          default:
+            break;
+          }
+        }
+      }
     }
   }
   
diff --git a/test/Transforms/InstCombine/fcmp-special.ll b/test/Transforms/InstCombine/fcmp-special.ll
new file mode 100644
index 00000000000..a39021e08d1
--- /dev/null
+++ b/test/Transforms/InstCombine/fcmp-special.ll
@@ -0,0 +1,155 @@
+; RUN: opt < %s -instcombine -S | FileCheck %s
+
+; Infinity
+
+; CHECK: inf0
+; CHECK: ret i1 false
+define i1 @inf0(double %arg) nounwind readnone {
+  %tmp = fcmp ogt double %arg, 0x7FF0000000000000
+  ret i1 %tmp
+}
+
+; CHECK: inf1
+; CHECK: ret i1 true
+define i1 @inf1(double %arg) nounwind readnone {
+  %tmp = fcmp ule double %arg, 0x7FF0000000000000
+  ret i1 %tmp
+}
+
+; Negative infinity
+
+; CHECK: ninf0
+; CHECK: ret i1 false
+define i1 @ninf0(double %arg) nounwind readnone {
+  %tmp = fcmp olt double %arg, 0xFFF0000000000000
+  ret i1 %tmp
+}
+
+; CHECK: ninf1
+; CHECK: ret i1 true
+define i1 @ninf1(double %arg) nounwind readnone {
+  %tmp = fcmp uge double %arg, 0xFFF0000000000000
+  ret i1 %tmp
+}
+
+; NaNs
+
+; CHECK: nan0
+; CHECK: ret i1 false
+define i1 @nan0(double %arg) nounwind readnone {
+  %tmp = fcmp ord double %arg, 0x7FF00000FFFFFFFF
+  ret i1 %tmp
+}
+
+; CHECK: nan1
+; CHECK: ret i1 false
+define i1 @nan1(double %arg) nounwind readnone {
+  %tmp = fcmp oeq double %arg, 0x7FF00000FFFFFFFF
+  ret i1 %tmp
+}
+
+; CHECK: nan2
+; CHECK: ret i1 false
+define i1 @nan2(double %arg) nounwind readnone {
+  %tmp = fcmp olt double %arg, 0x7FF00000FFFFFFFF
+  ret i1 %tmp
+}
+
+; CHECK: nan3
+; CHECK: ret i1 true
+define i1 @nan3(double %arg) nounwind readnone {
+  %tmp = fcmp uno double %arg, 0x7FF00000FFFFFFFF
+  ret i1 %tmp
+}
+
+; CHECK: nan4
+; CHECK: ret i1 true
+define i1 @nan4(double %arg) nounwind readnone {
+  %tmp = fcmp une double %arg, 0x7FF00000FFFFFFFF
+  ret i1 %tmp
+}
+
+; CHECK: nan5
+; CHECK: ret i1 true
+define i1 @nan5(double %arg) nounwind readnone {
+  %tmp = fcmp ult double %arg, 0x7FF00000FFFFFFFF
+  ret i1 %tmp
+}
+
+; Negative NaN.
+
+; CHECK: nnan0
+; CHECK: ret i1 false
+define i1 @nnan0(double %arg) nounwind readnone {
+  %tmp = fcmp ord double %arg, 0xFFF00000FFFFFFFF
+  ret i1 %tmp
+}
+
+; CHECK: nnan1
+; CHECK: ret i1 false
+define i1 @nnan1(double %arg) nounwind readnone {
+  %tmp = fcmp oeq double %arg, 0xFFF00000FFFFFFFF
+  ret i1 %tmp
+}
+
+; CHECK: nnan2
+; CHECK: ret i1 false
+define i1 @nnan2(double %arg) nounwind readnone {
+  %tmp = fcmp olt double %arg, 0xFFF00000FFFFFFFF
+  ret i1 %tmp
+}
+
+; CHECK: nnan3
+; CHECK: ret i1 true
+define i1 @nnan3(double %arg) nounwind readnone {
+  %tmp = fcmp uno double %arg, 0xFFF00000FFFFFFFF
+  ret i1 %tmp
+}
+
+; CHECK: nnan4
+; CHECK: ret i1 true
+define i1 @nnan4(double %arg) nounwind readnone {
+  %tmp = fcmp une double %arg, 0xFFF00000FFFFFFFF
+  ret i1 %tmp
+}
+
+; CHECK: nnan5
+; CHECK: ret i1 true
+define i1 @nnan5(double %arg) nounwind readnone {
+  %tmp = fcmp ult double %arg, 0xFFF00000FFFFFFFF
+  ret i1 %tmp
+}
+
+; Negative zero.
+
+; CHECK: nzero0
+; CHECK: ret i1 true
+define i1 @nzero0() {
+  %tmp = fcmp oeq double 0.0, -0.0
+  ret i1 %tmp
+}
+
+; CHECK: nzero1
+; CHECK: ret i1 false
+define i1 @nzero1() {
+  %tmp = fcmp ogt double 0.0, -0.0
+  ret i1 %tmp
+}
+
+; Misc.
+
+; CHECK: misc0
+; CHECK: %tmp = fcmp ord double %arg, 0.000000e+00
+; CHECK: ret i1 %tmp
+define i1 @misc0(double %arg) {
+  %tmp = fcmp oeq double %arg, %arg
+  ret i1 %tmp
+}
+
+; CHECK: misc1
+; CHECK: ret i1 false
+define i1 @misc1(double %arg) {
+  %tmp = fcmp one double %arg, %arg
+  ret i1 %tmp
+}
+