diff options
| -rw-r--r-- | lib/Target/X86/README.txt | 37 | ||||
| -rw-r--r-- | lib/Transforms/InstCombine/InstCombineCompares.cpp | 10 | ||||
| -rw-r--r-- | test/Transforms/InstCombine/icmp.ll | 17 |
3 files changed, 27 insertions, 37 deletions
diff --git a/lib/Target/X86/README.txt b/lib/Target/X86/README.txt index 6a8a4fd..b4285a0 100644 --- a/lib/Target/X86/README.txt +++ b/lib/Target/X86/README.txt @@ -1568,43 +1568,6 @@ The second one is done for: Atom, Pentium Pro, all AMDs, Pentium 4, Nocona, Core 2, and "Generic" //===---------------------------------------------------------------------===// - -Testcase: -int a(int x) { return (x & 127) > 31; } - -Current output: - movl 4(%esp), %eax - andl $127, %eax - cmpl $31, %eax - seta %al - movzbl %al, %eax - ret - -Ideal output: - xorl %eax, %eax - testl $96, 4(%esp) - setne %al - ret - -This should definitely be done in instcombine, canonicalizing the range -condition into a != condition. We get this IR: - -define i32 @a(i32 %x) nounwind readnone { -entry: - %0 = and i32 %x, 127 ; <i32> [#uses=1] - %1 = icmp ugt i32 %0, 31 ; <i1> [#uses=1] - %2 = zext i1 %1 to i32 ; <i32> [#uses=1] - ret i32 %2 -} - -Instcombine prefers to strength reduce relational comparisons to equality -comparisons when possible, this should be another case of that. This could -be handled pretty easily in InstCombiner::visitICmpInstWithInstAndIntCst, but it -looks like InstCombiner::visitICmpInstWithInstAndIntCst should really already -be redesigned to use ComputeMaskedBits and friends. - - -//===---------------------------------------------------------------------===// Testcase: int x(int a) { return (a&0xf0)>>4; } diff --git a/lib/Transforms/InstCombine/InstCombineCompares.cpp b/lib/Transforms/InstCombine/InstCombineCompares.cpp index 1b96c3c..13516d1 100644 --- a/lib/Transforms/InstCombine/InstCombineCompares.cpp +++ b/lib/Transforms/InstCombine/InstCombineCompares.cpp @@ -1226,6 +1226,16 @@ Instruction *InstCombiner::visitICmpInstWithInstAndIntCst(ICmpInst &ICI, ICI.setOperand(0, NewAnd); return &ICI; } + + // Replace ((X & AndCST) > RHSV) with ((X & AndCST) != 0), if any + // bit set in (X & AndCST) will produce a result greater than RHSV. + if (ICI.getPredicate() == ICmpInst::ICMP_UGT) { + unsigned NTZ = AndCST->getValue().countTrailingZeros(); + if ((NTZ < AndCST->getBitWidth()) && + APInt::getOneBitSet(AndCST->getBitWidth(), NTZ).ugt(RHSV)) + return new ICmpInst(ICmpInst::ICMP_NE, LHSI, + Constant::getNullValue(RHS->getType())); + } } // Try to optimize things like "A[i]&42 == 0" to index computations. diff --git a/test/Transforms/InstCombine/icmp.ll b/test/Transforms/InstCombine/icmp.ll index 8e064a4..138b10e 100644 --- a/test/Transforms/InstCombine/icmp.ll +++ b/test/Transforms/InstCombine/icmp.ll @@ -677,3 +677,20 @@ define i1 @test66(i64 %A, i64 %B) { ; CHECK-NEXT: ret i1 true ret i1 %cmp } + +; CHECK: @test67 +; CHECK: %and = and i32 %x, 96 +; CHECK: %cmp = icmp ne i32 %and, 0 +define i1 @test67(i32 %x) nounwind uwtable { + %and = and i32 %x, 127 + %cmp = icmp sgt i32 %and, 31 + ret i1 %cmp +} + +; CHECK: @test68 +; CHECK: %cmp = icmp ugt i32 %and, 30 +define i1 @test68(i32 %x) nounwind uwtable { + %and = and i32 %x, 127 + %cmp = icmp sgt i32 %and, 30 + ret i1 %cmp +} |