}
}
+ // See if we can determine the result of this select based on a dominating
+ // condition.
+ BasicBlock *Parent = SI.getParent();
+ if (BasicBlock *Dom = Parent->getSinglePredecessor()) {
+ auto *PBI = dyn_cast_or_null<BranchInst>(Dom->getTerminator());
+ if (PBI && PBI->isConditional() &&
+ PBI->getSuccessor(0) != PBI->getSuccessor(1) &&
+ (PBI->getSuccessor(0) == Parent || PBI->getSuccessor(1) == Parent)) {
+ bool CondIsFalse = PBI->getSuccessor(1) == Parent;
+ Optional<bool> Implication = isImpliedCondition(
+ PBI->getCondition(), SI.getCondition(), DL, CondIsFalse);
+ if (Implication) {
+ Value *V = *Implication ? TrueVal : FalseVal;
+ return replaceInstUsesWith(SI, V);
+ }
+ }
+ }
+
return nullptr;
}
--- /dev/null
+; RUN: opt < %s -instcombine -S | FileCheck %s
+
+; A == B implies A >u B is false.
+; CHECK-LABEL: @test1
+; CHECK-NOT: select
+; CHECK: call void @foo(i32 10)
+define void @test1(i32 %a, i32 %b) {
+ %cmp1 = icmp eq i32 %a, %b
+ br i1 %cmp1, label %taken, label %end
+
+taken:
+ %cmp2 = icmp ugt i32 %a, %b
+ %c = select i1 %cmp2, i32 0, i32 10
+ call void @foo(i32 %c)
+ br label %end
+
+end:
+ ret void
+}
+
+; If A == B is false then A != B is true.
+; CHECK-LABEL: @test2
+; CHECK-NOT: select
+; CHECK: call void @foo(i32 20)
+define void @test2(i32 %a, i32 %b) {
+ %cmp1 = icmp eq i32 %a, %b
+ br i1 %cmp1, label %end, label %taken
+
+taken:
+ %cmp2 = icmp ne i32 %a, %b
+ %c = select i1 %cmp2, i32 20, i32 0
+ call void @foo(i32 %c)
+ br label %end
+
+end:
+ ret void
+}
+
+; A >u 10 implies A >u 10 is true.
+; CHECK-LABEL: @test3
+; CHECK-NOT: select
+; CHECK: call void @foo(i32 30)
+define void @test3(i32 %a, i32 %b) {
+ %cmp1 = icmp ugt i32 %a, 10
+ br i1 %cmp1, label %taken, label %end
+
+taken:
+ %cmp2 = icmp ugt i32 %a, 10
+ %c = select i1 %cmp2, i32 30, i32 0
+ call void @foo(i32 %c)
+ br label %end
+
+end:
+ ret void
+}
+
+; CHECK-LABEL: @PR23333
+; CHECK-NOT: select
+; CHECK: ret i8 1
+define i8 @PR23333(i8 addrspace(1)* %ptr) {
+ %cmp = icmp eq i8 addrspace(1)* %ptr, null
+ br i1 %cmp, label %taken, label %end
+
+taken:
+ %cmp2 = icmp ne i8 addrspace(1)* %ptr, null
+ %res = select i1 %cmp2, i8 2, i8 1
+ ret i8 %res
+
+end:
+ ret i8 0
+}
+
+; We know the condition of the select is true based on a dominating condition.
+; Therefore, we can replace %cond with %len.
+; CHECK-LABEL: @test4
+; CHECK-NOT: select
+define void @test4(i32 %len) {
+entry:
+ %0 = call i32 @bar(i32 %len);
+ %cmp = icmp ult i32 %len, 4
+ br i1 %cmp, label %bb, label %b1
+bb:
+ %cond = select i1 %cmp, i32 %len, i32 8
+; CHECK: %cmp11 = icmp eq i32 %len, 8
+ %cmp11 = icmp eq i32 %cond, 8
+ br i1 %cmp11, label %b0, label %b1
+
+b0:
+ call void @foo(i32 %len)
+ br label %b1
+
+b1:
+; CHECK: phi i32 [ %len, %bb ], [ undef, %b0 ], [ %0, %entry ]
+ %1 = phi i32 [ %cond, %bb ], [ undef, %b0 ], [ %0, %entry ]
+ br label %ret
+
+ret:
+ call void @foo(i32 %1)
+ ret void
+}
+
+declare void @foo(i32)
+declare i32 @bar(i32)