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llvm-mirror/test/Transforms/Inline/inline_constprop.ll
Chandler Carruth f3295eafa5 Fix a stunning oversight in the inline cost analysis. It was never
propagating one of the values it simplified to a constant across
a myriad of instructions. Notably, ptrtoint instructions when we had
a constant pointer (say, 0) didn't propagate that, blocking a massive
number of down-stream optimizations.

This was uncovered when investigating why we fail to inline and delete
the boilerplate in:

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

It turns out most of the efforts I've made thus far to improve the
analysis weren't making it far purely because of this. After this is
fixed, the store-to-load forwarding patch enables LLVM to optimize the
above to an empty function. We still can't nuke a second push_back, but
for different reasons.

There is a very real chance this will cause somewhat noticable changes
in inlining behavior, so please let me know if you see regressions (or
improvements!) because of this patch.

llvm-svn: 171196
2012-12-28 14:43:42 +00:00

251 lines
5.9 KiB
LLVM

; RUN: opt < %s -inline -inline-threshold=20 -S | FileCheck %s
define internal i32 @callee1(i32 %A, i32 %B) {
%C = sdiv i32 %A, %B
ret i32 %C
}
define i32 @caller1() {
; CHECK: define i32 @caller1
; CHECK-NEXT: ret i32 3
%X = call i32 @callee1( i32 10, i32 3 )
ret i32 %X
}
define i32 @caller2() {
; Check that we can constant-prop through instructions after inlining callee21
; to get constants in the inlined callsite to callee22.
; FIXME: Currently, the threshold is fixed at 20 because we don't perform
; *recursive* cost analysis to realize that the nested call site will definitely
; inline and be cheap. We should eventually do that and lower the threshold here
; to 1.
;
; CHECK: @caller2
; CHECK-NOT: call void @callee2
; CHECK: ret
%x = call i32 @callee21(i32 42, i32 48)
ret i32 %x
}
define i32 @callee21(i32 %x, i32 %y) {
%sub = sub i32 %y, %x
%result = call i32 @callee22(i32 %sub)
ret i32 %result
}
declare i8* @getptr()
define i32 @callee22(i32 %x) {
%icmp = icmp ugt i32 %x, 42
br i1 %icmp, label %bb.true, label %bb.false
bb.true:
; This block musn't be counted in the inline cost.
%x1 = add i32 %x, 1
%x2 = add i32 %x1, 1
%x3 = add i32 %x2, 1
%x4 = add i32 %x3, 1
%x5 = add i32 %x4, 1
%x6 = add i32 %x5, 1
%x7 = add i32 %x6, 1
%x8 = add i32 %x7, 1
ret i32 %x8
bb.false:
ret i32 %x
}
define i32 @caller3() {
; Check that even if the expensive path is hidden behind several basic blocks,
; it doesn't count toward the inline cost when constant-prop proves those paths
; dead.
;
; CHECK: @caller3
; CHECK-NOT: call
; CHECK: ret i32 6
entry:
%x = call i32 @callee3(i32 42, i32 48)
ret i32 %x
}
define i32 @callee3(i32 %x, i32 %y) {
%sub = sub i32 %y, %x
%icmp = icmp ugt i32 %sub, 42
br i1 %icmp, label %bb.true, label %bb.false
bb.true:
%icmp2 = icmp ult i32 %sub, 64
br i1 %icmp2, label %bb.true.true, label %bb.true.false
bb.true.true:
; This block musn't be counted in the inline cost.
%x1 = add i32 %x, 1
%x2 = add i32 %x1, 1
%x3 = add i32 %x2, 1
%x4 = add i32 %x3, 1
%x5 = add i32 %x4, 1
%x6 = add i32 %x5, 1
%x7 = add i32 %x6, 1
%x8 = add i32 %x7, 1
br label %bb.merge
bb.true.false:
; This block musn't be counted in the inline cost.
%y1 = add i32 %y, 1
%y2 = add i32 %y1, 1
%y3 = add i32 %y2, 1
%y4 = add i32 %y3, 1
%y5 = add i32 %y4, 1
%y6 = add i32 %y5, 1
%y7 = add i32 %y6, 1
%y8 = add i32 %y7, 1
br label %bb.merge
bb.merge:
%result = phi i32 [ %x8, %bb.true.true ], [ %y8, %bb.true.false ]
ret i32 %result
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 i64 @caller5(i64 %y) {
; Check that we can round trip constants through various kinds of casts etc w/o
; losing track of the constant prop in the inline cost analysis.
;
; CHECK: @caller5
; CHECK-NOT: call
; CHECK: ret i64 -1
entry:
%x = call i64 @callee5(i64 42, i64 %y)
ret i64 %x
}
define i64 @callee5(i64 %x, i64 %y) {
%inttoptr = inttoptr i64 %x to i8*
%bitcast = bitcast i8* %inttoptr to i32*
%ptrtoint = ptrtoint i32* %bitcast to i64
%trunc = trunc i64 %ptrtoint to i32
%zext = zext i32 %trunc to i64
%cmp = icmp eq i64 %zext, 42
br i1 %cmp, label %bb.true, label %bb.false
bb.true:
ret i64 -1
bb.false:
; This block musn't be counted in the inline cost.
%y1 = add i64 %y, 1
%y2 = add i64 %y1, 1
%y3 = add i64 %y2, 1
%y4 = add i64 %y3, 1
%y5 = add i64 %y4, 1
%y6 = add i64 %y5, 1
%y7 = add i64 %y6, 1
%y8 = add i64 %y7, 1
ret i64 %y8
}
define i32 @PR13412.main() {
; This is a somewhat complicated three layer subprogram that was reported to
; compute the wrong value for a branch due to assuming that an argument
; mid-inline couldn't be equal to another pointer.
;
; After inlining, the branch should point directly to the exit block, not to
; the intermediate block.
; CHECK: @PR13412.main
; CHECK: br i1 true, label %[[TRUE_DEST:.*]], label %[[FALSE_DEST:.*]]
; CHECK: [[FALSE_DEST]]:
; CHECK-NEXT: call void @PR13412.fail()
; CHECK: [[TRUE_DEST]]:
; CHECK-NEXT: ret i32 0
entry:
%i1 = alloca i64
store i64 0, i64* %i1
%arraydecay = bitcast i64* %i1 to i32*
%call = call i1 @PR13412.first(i32* %arraydecay, i32* %arraydecay)
br i1 %call, label %cond.end, label %cond.false
cond.false:
call void @PR13412.fail()
br label %cond.end
cond.end:
ret i32 0
}
define internal i1 @PR13412.first(i32* %a, i32* %b) {
entry:
%call = call i32* @PR13412.second(i32* %a, i32* %b)
%cmp = icmp eq i32* %call, %b
ret i1 %cmp
}
declare void @PR13412.fail()
define internal i32* @PR13412.second(i32* %a, i32* %b) {
entry:
%sub.ptr.lhs.cast = ptrtoint i32* %b to i64
%sub.ptr.rhs.cast = ptrtoint i32* %a to i64
%sub.ptr.sub = sub i64 %sub.ptr.lhs.cast, %sub.ptr.rhs.cast
%sub.ptr.div = ashr exact i64 %sub.ptr.sub, 2
%cmp = icmp ugt i64 %sub.ptr.div, 1
br i1 %cmp, label %if.then, label %if.end3
if.then:
%0 = load i32* %a
%1 = load i32* %b
%cmp1 = icmp eq i32 %0, %1
br i1 %cmp1, label %return, label %if.end3
if.end3:
br label %return
return:
%retval.0 = phi i32* [ %b, %if.end3 ], [ %a, %if.then ]
ret i32* %retval.0
}