InstCombine: Add a few missing combines for ANDs and ORs of sign bit tests.

On x86 we now compile "if (a < 0 && b < 0)" into
	testl	%edi, %esi
	js	IF.THEN

llvm-svn: 128496

1 files changed, 24 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
index c8545f5deec..1cb18e12eef 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
@@ -756,6 +756,18 @@ Value *InstCombiner::FoldAndOfICmps(ICmpInst *LHS, ICmpInst *RHS) {
       Value *NewOr = Builder->CreateOr(Val, Val2);
       return Builder->CreateICmp(LHSCC, NewOr, LHSCst);
     }
+
+    // (icmp slt A, 0) & (icmp slt B, 0) --> (icmp slt (A&B), 0)
+    if (LHSCC == ICmpInst::ICMP_SLT && LHSCst->isZero()) {
+      Value *NewAnd = Builder->CreateAnd(Val, Val2);
+      return Builder->CreateICmp(LHSCC, NewAnd, LHSCst);
+    }
+
+    // (icmp sgt A, -1) & (icmp sgt B, -1) --> (icmp sgt (A|B), -1)
+    if (LHSCC == ICmpInst::ICMP_SGT && LHSCst->isAllOnesValue()) {
+      Value *NewOr = Builder->CreateOr(Val, Val2);
+      return Builder->CreateICmp(LHSCC, NewOr, LHSCst);
+    }
   }
   
   // From here on, we only handle:
@@ -1442,6 +1454,18 @@ Value *InstCombiner::FoldOrOfICmps(ICmpInst *LHS, ICmpInst *RHS) {
       Value *NewOr = Builder->CreateOr(Val, Val2);
       return Builder->CreateICmp(LHSCC, NewOr, LHSCst);
     }
+
+    // (icmp slt A, 0) | (icmp slt B, 0) --> (icmp slt (A|B), 0)
+    if (LHSCC == ICmpInst::ICMP_SLT && LHSCst->isZero()) {
+      Value *NewOr = Builder->CreateOr(Val, Val2);
+      return Builder->CreateICmp(LHSCC, NewOr, LHSCst);
+    }
+
+    // (icmp sgt A, -1) | (icmp sgt B, -1) --> (icmp sgt (A&B), -1)
+    if (LHSCC == ICmpInst::ICMP_SGT && LHSCst->isAllOnesValue()) {
+      Value *NewAnd = Builder->CreateAnd(Val, Val2);
+      return Builder->CreateICmp(LHSCC, NewAnd, LHSCst);
+    }
   }
 
   // (icmp ult (X + CA), C1) | (icmp eq X, C2) -> (icmp ule (X + CA), C1)