Teach the inline cost analysis about calls that can be simplified and

how to propagate constants through insert and extract value
instructions.

With the recent improvements to instsimplify, this allows inline cost
analysis to constant fold through intrinsic functions, including notably
the with.overflow intrinsic math routines which often show up inside of
STL abstractions. This is yet another piece in the puzzle of breaking
down the code for:

  void f() {
    std::vector<int> v;
    v.push_back(1);
  }

But it still isn't enough. There are a pile of bugs in inline cost still
blocking this.

llvm-svn: 171195

1 files changed, 38 insertions, 0 deletions

diff --git a/llvm/test/Transforms/Inline/inline_constprop.ll b/llvm/test/Transforms/Inline/inline_constprop.ll
index 0b48a7282f4..b2a14fe0b71 100644
--- a/llvm/test/Transforms/Inline/inline_constprop.ll
+++ b/llvm/test/Transforms/Inline/inline_constprop.ll
@@ -111,6 +111,44 @@ bb.false:
   ret i32 %sub
 }
 
+declare {i8, i1} @llvm.uadd.with.overflow.i8(i8 %a, i8 %b)
+
+define i8 @caller4(i8 %z) {
+; Check that we can constant fold through intrinsics such as the
+; overflow-detecting arithmetic instrinsics. These are particularly important
+; as they are used heavily in standard library code and generic C++ code where
+; the arguments are oftent constant but complete generality is required.
+;
+; CHECK: @caller4
+; CHECK-NOT: call
+; CHECK: ret i8 -1
+
+entry:
+  %x = call i8 @callee4(i8 254, i8 14, i8 %z)
+  ret i8 %x
+}
+
+define i8 @callee4(i8 %x, i8 %y, i8 %z) {
+  %uadd = call {i8, i1} @llvm.uadd.with.overflow.i8(i8 %x, i8 %y)
+  %o = extractvalue {i8, i1} %uadd, 1
+  br i1 %o, label %bb.true, label %bb.false
+
+bb.true:
+  ret i8 -1
+
+bb.false:
+  ; This block musn't be counted in the inline cost.
+  %z1 = add i8 %z, 1
+  %z2 = add i8 %z1, 1
+  %z3 = add i8 %z2, 1
+  %z4 = add i8 %z3, 1
+  %z5 = add i8 %z4, 1
+  %z6 = add i8 %z5, 1
+  %z7 = add i8 %z6, 1
+  %z8 = add i8 %z7, 1
+  ret i8 %z8
+}
+
 
 define i32 @PR13412.main() {
 ; This is a somewhat complicated three layer subprogram that was reported to