[llvm-commits] [llvm] r126744 - in /llvm/trunk: lib/Transforms/InstCombine/InstCombineAndOrXor.cpp test/Transforms/InstCombine/and2.ll

[Anders Carlsson]

Author: andersca
Date: Tue Mar  1 09:05:01 2011
New Revision: 126744

URL: http://llvm.org/viewvc/llvm-project?rev=126744&view=rev
Log:
Make InstCombiner::FoldAndOfICmps create a ConstantRange that's the
intersection of the LHS and RHS ConstantRanges and return "false" when
the range is empty.

This simplifies some code and catches some extra cases.

Modified:
    llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
    llvm/trunk/test/Transforms/InstCombine/and2.ll

Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp?rev=126744&r1=126743&r2=126744&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp Tue Mar  1 09:05:01 2011
@@ -14,6 +14,7 @@
 #include "InstCombine.h"
 #include "llvm/Intrinsics.h"
 #include "llvm/Analysis/InstructionSimplify.h"
+#include "llvm/Support/ConstantRange.h"
 #include "llvm/Support/PatternMatch.h"
 using namespace llvm;
 using namespace PatternMatch;
@@ -767,7 +768,17 @@
       LHSCC == ICmpInst::ICMP_SGE || LHSCC == ICmpInst::ICMP_SLE ||
       RHSCC == ICmpInst::ICMP_SGE || RHSCC == ICmpInst::ICMP_SLE)
     return 0;
-  
+
+  // Make a constant range that's the intersection of the two icmp ranges.
+  // If the intersection is empty, we know that the result is false.
+  ConstantRange LHSRange = 
+    ConstantRange::makeICmpRegion(LHSCC, LHSCst->getValue());
+  ConstantRange RHSRange = 
+    ConstantRange::makeICmpRegion(RHSCC, RHSCst->getValue());
+
+  if (LHSRange.intersectWith(RHSRange).isEmptySet())
+    return ConstantInt::get(CmpInst::makeCmpResultType(LHS->getType()), 0);
+
   // We can't fold (ugt x, C) & (sgt x, C2).
   if (!PredicatesFoldable(LHSCC, RHSCC))
     return 0;
@@ -800,10 +811,6 @@
   case ICmpInst::ICMP_EQ:
     switch (RHSCC) {
     default: llvm_unreachable("Unknown integer condition code!");
-    case ICmpInst::ICMP_EQ:         // (X == 13 & X == 15) -> false
-    case ICmpInst::ICMP_UGT:        // (X == 13 & X >  15) -> false
-    case ICmpInst::ICMP_SGT:        // (X == 13 & X >  15) -> false
-      return ConstantInt::get(CmpInst::makeCmpResultType(LHS->getType()), 0);
     case ICmpInst::ICMP_NE:         // (X == 13 & X != 15) -> X == 13
     case ICmpInst::ICMP_ULT:        // (X == 13 & X <  15) -> X == 13
     case ICmpInst::ICMP_SLT:        // (X == 13 & X <  15) -> X == 13
@@ -851,9 +858,6 @@
   case ICmpInst::ICMP_SLT:
     switch (RHSCC) {
     default: llvm_unreachable("Unknown integer condition code!");
-    case ICmpInst::ICMP_EQ:         // (X s< 13 & X == 15) -> false
-    case ICmpInst::ICMP_SGT:        // (X s< 13 & X s> 15) -> false
-      return ConstantInt::get(CmpInst::makeCmpResultType(LHS->getType()), 0);
     case ICmpInst::ICMP_UGT:        // (X s< 13 & X u> 15) -> no change
       break;
     case ICmpInst::ICMP_NE:         // (X s< 13 & X != 15) -> X < 13

Modified: llvm/trunk/test/Transforms/InstCombine/and2.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/and2.ll?rev=126744&r1=126743&r2=126744&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/and2.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/and2.ll Tue Mar  1 09:05:01 2011
@@ -26,3 +26,12 @@
 ; CHECK-NEXT: and i32 %X, %Y
 ; CHECK-NEXT: ret
 }
+
+define i1 @test4(i32 %X) {
+  %a = icmp ult i32 %X, 31
+  %b = icmp slt i32 %X, 0
+  %c = and i1 %a, %b
+  ret i1 %c
+; CHECK: @test4
+; CHECK-NEXT: ret i1 false
+}