Teach InstCombine to merge (icmp ult (X + CA), C1) | (icmp eq X, C2) into (icmp ult (X + CA), C1 + 1) if C2 + CA == C1.
InstCombine creates these so now we compile x == 23 || x == 24 || x == 25 to
%x.off = add i32 %x, -23
%1 = icmp ult i32 %x.off, 3
instead of
%x.off = add i32 %x, -23
%1 = icmp ult i32 %x.off, 2
%cmp3 = icmp eq i32 %x, 25
%ret2 = or i1 %1, %cmp3
llvm-svn: 122248
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
index 41734f6..57fe870 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
@@ -1450,7 +1450,16 @@
return Builder->CreateICmp(LHSCC, NewOr, LHSCst);
}
}
-
+
+ // (icmp ult (X + CA), C1) | (icmp eq X, C2) -> (icmp ult (X + CA), C1 + 1)
+ // iff C2 + CA == C1.
+ if (LHSCC == ICmpInst::ICMP_ULT) {
+ ConstantInt *AddCst;
+ if (match(Val, m_Add(m_Specific(Val2), m_ConstantInt(AddCst))))
+ if (RHSCst->getValue() + AddCst->getValue() == LHSCst->getValue())
+ return Builder->CreateICmp(LHSCC, Val, AddOne(LHSCst));
+ }
+
// From here on, we only handle:
// (icmp1 A, C1) | (icmp2 A, C2) --> something simpler.
if (Val != Val2) return 0;
diff --git a/llvm/test/Transforms/InstCombine/or.ll b/llvm/test/Transforms/InstCombine/or.ll
index 500cad2..f82f9fa 100644
--- a/llvm/test/Transforms/InstCombine/or.ll
+++ b/llvm/test/Transforms/InstCombine/or.ll
@@ -376,3 +376,17 @@
; CHECK-NEXT: or i32 %a, %b
; CHECK-NEXT: or i32 %1, 1135
}
+
+define i1 @test36(i32 %x) {
+ %cmp1 = icmp eq i32 %x, 23
+ %cmp2 = icmp eq i32 %x, 24
+ %ret1 = or i1 %cmp1, %cmp2
+ %cmp3 = icmp eq i32 %x, 25
+ %ret2 = or i1 %ret1, %cmp3
+ ret i1 %ret2
+; CHECK: @test36
+; CHECK-NEXT: %x.off = add i32 %x, -23
+; CHECK-NEXT: icmp ult i32 %x.off, 3
+; CHECK-NEXT: ret i1
+}
+