static Instruction *ProcessUGT_ADDCST_ADD(ICmpInst &I, Value *A, Value *B,
ConstantInt *CI2, ConstantInt *CI1,
InstCombiner::BuilderTy *Builder) {
+ // The transformation we're trying to do here is to transform this into an
+ // llvm.sadd.with.overflow. To do this, we have to replace the original add
+ // with a narrower add, and discard the add-with-constant that is part of the
+ // range check (if we can't eliminate it, this isn't profitable).
+
+ // In order to eliminate the add-with-constant, the compare can be its only
+ // use.
+ Value *AddWithCst = I.getOperand(0);
+ if (!AddWithCst->hasOneUse()) return 0;
+
const IntegerType *WideType = cast<IntegerType>(CI1->getType());
unsigned WideWidth = WideType->getBitWidth();
unsigned NarrowWidth = WideWidth / 2;
; RUN: opt -S -instcombine < %s | FileCheck %s
; <rdar://problem/8558713>
+declare i32 @throwAnExceptionOrWhatever(...)
+
; CHECK: @test1
define i32 @test1(i32 %a, i32 %b) nounwind ssp {
entry:
ret i32 %conv9
}
-declare i32 @throwAnExceptionOrWhatever(...)
+; CHECK: @test2
+; This form should not be promoted for two reasons: 1) it is unprofitable to
+; promote it since the add.off instruction has another use, and 2) it is unsafe
+; because the add-with-off makes the high bits of the original add live.
+define i32 @test2(i32 %a, i32 %b, i64* %P) nounwind ssp {
+entry:
+ %conv = sext i32 %a to i64
+ %conv2 = sext i32 %b to i64
+ %add = add nsw i64 %conv2, %conv
+ %add.off = add i64 %add, 2147483648
+
+ store i64 %add.off, i64* %P
+
+; CHECK-NOT: llvm.sadd.with.overflow
+ %0 = icmp ugt i64 %add.off, 4294967295
+ br i1 %0, label %if.then, label %if.end
+
+if.then:
+ %call = tail call i32 (...)* @throwAnExceptionOrWhatever() nounwind
+ br label %if.end
+
+if.end:
+ %conv9 = trunc i64 %add to i32
+; CHECK: ret i32
+ ret i32 %conv9
+}
+