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

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@128496 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 103 insertions, 0 deletions

diff --git a/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp b/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
index c8545f5dee..1cb18e12ee 100644
--- a/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
+++ b/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)
diff --git a/test/Transforms/InstCombine/sign-test-and-or.ll b/test/Transforms/InstCombine/sign-test-and-or.ll
new file mode 100644
index 0000000000..47f5f3051e
--- /dev/null
+++ b/test/Transforms/InstCombine/sign-test-and-or.ll
@@ -0,0 +1,79 @@
+; RUN: opt -S -instcombine < %s | FileCheck %s
+
+declare void @foo()
+
+define void @test1(i32 %a, i32 %b) nounwind {
+  %1 = icmp slt i32 %a, 0
+  %2 = icmp slt i32 %b, 0
+  %or.cond = or i1 %1, %2
+  br i1 %or.cond, label %if.then, label %if.end
+
+; CHECK: @test1
+; CHECK-NEXT: %1 = or i32 %a, %b
+; CHECK-NEXT: %2 = icmp slt i32 %1, 0
+; CHECK-NEXT: br
+
+if.then:
+  tail call void @foo() nounwind
+  ret void
+
+if.end:
+  ret void
+}
+
+define void @test2(i32 %a, i32 %b) nounwind {
+  %1 = icmp sgt i32 %a, -1
+  %2 = icmp sgt i32 %b, -1
+  %or.cond = or i1 %1, %2
+  br i1 %or.cond, label %if.then, label %if.end
+
+; CHECK: @test2
+; CHECK-NEXT: %1 = and i32 %a, %b
+; CHECK-NEXT: %2 = icmp sgt i32 %1, -1
+; CHECK-NEXT: br
+
+if.then:
+  tail call void @foo() nounwind
+  ret void
+
+if.end:
+  ret void
+}
+
+define void @test3(i32 %a, i32 %b) nounwind {
+  %1 = icmp slt i32 %a, 0
+  %2 = icmp slt i32 %b, 0
+  %or.cond = and i1 %1, %2
+  br i1 %or.cond, label %if.then, label %if.end
+
+; CHECK: @test3
+; CHECK-NEXT: %1 = and i32 %a, %b
+; CHECK-NEXT: %2 = icmp slt i32 %1, 0
+; CHECK-NEXT: br
+
+if.then:
+  tail call void @foo() nounwind
+  ret void
+
+if.end:
+  ret void
+}
+
+define void @test4(i32 %a, i32 %b) nounwind {
+  %1 = icmp sgt i32 %a, -1
+  %2 = icmp sgt i32 %b, -1
+  %or.cond = and i1 %1, %2
+  br i1 %or.cond, label %if.then, label %if.end
+
+; CHECK: @test4
+; CHECK-NEXT: %1 = or i32 %a, %b
+; CHECK-NEXT: %2 = icmp sgt i32 %1, -1
+; CHECK-NEXT: br
+
+if.then:
+  tail call void @foo() nounwind
+  ret void
+
+if.end:
+  ret void
+}