[llvm] r286814 - [InlineCost] Remove skew when calculating call costs
Xinliang David Li via llvm-commits
llvm-commits at lists.llvm.org
Tue Nov 15 23:19:22 PST 2016
On Tue, Nov 15, 2016 at 7:01 PM, Gerolf Hoflehner via llvm-commits <
llvm-commits at lists.llvm.org> wrote:
> The compiler should certainly inline the test case, but there seems to be
> a high compile-time/code size cost on average for Os/O2. It would be great
> to have a clearer picture of the performance gains for the costs. I also
> hope to get a few eyes on the code review from inliner experts. It is not
> clear to me that the fix is the correct solution to the problem:
>
> There are 3 uses of call penalty after this commit: when the call cost is
> estimated it is added, but for the benefits instr cost + call penalty is
> subtracted. Shouldn’t it be one of instr cost, call penalty or instr cost +
> call penalty in both cases?
>
In call cost computation, Instrcost is also added. See analyzeBlock at the
callsite where instruction visitor is invoked: if it is not simplified, the
cost is added.
David
>
> This is all about raising awareness. if the consensus is this is this fix
> is right thing to do cost is just something to be aware of and move on.
>
> Thanks
> Gerolf
>
> PS (more out of curiosity):
>
> Also, and this is somewhat orthogonal to the specific change, but I
> noticed the use of CallPenalty in the following case:
>
> if (TTI.getFPOpCost(I->getType()) == TargetTransformInfo::TCC_Expensive ||
> hasSoftFloatAttr) Cost += InlineConstants::CallPenalty; Why is
> CallPenalty a good cost estimate under this condition?
>
> On Nov 14, 2016, at 5:48 PM, Mikhail Zolotukhin <mzolotukhin at apple.com>
> wrote:
>
> Hi James,
>
> Green dragon detected some big regressions, most probably from your change
> (up to 30% code size and compile time regressions on ARM64 [1] and x86
> [2]). Did you plan to tweak the thresholds after the change?
>
> Thanks,
> Michael
>
> [1] ARM64, Os: http://104.154.54.203/db_default/v4/nts/13248
> [2] x86, O3+flto: http://104.154.54.203/db_default/v4/nts/13245
>
>
> On Nov 14, 2016, at 3:14 AM, James Molloy via llvm-commits <
> llvm-commits at lists.llvm.org> wrote:
>
> Author: jamesm
> Date: Mon Nov 14 05:14:41 2016
> New Revision: 286814
>
> URL: http://llvm.org/viewvc/llvm-project?rev=286814&view=rev
> Log:
> [InlineCost] Remove skew when calculating call costs
>
> When calculating the cost of a call instruction we were applying a
> heuristic penalty as well as the cost of the instruction itself.
>
> However, when calculating the benefit from inlining we weren't discounting
> the equivalent penalty for the call instruction that would be removed! This
> caused skew in the calculation and meant we wouldn't inline in the
> following, trivial case:
>
> int g() {
> h();
> }
> int f() {
> g();
> }
>
> Modified:
> llvm/trunk/lib/Analysis/InlineCost.cpp
> llvm/trunk/test/Transforms/Inline/alloca-bonus.ll
> llvm/trunk/test/Transforms/Inline/inline-cold-callee.ll
> llvm/trunk/test/Transforms/Inline/inline-cold.ll
> llvm/trunk/test/Transforms/Inline/inline-hot-callee.ll
> llvm/trunk/test/Transforms/Inline/inline-hot-callsite.ll
> llvm/trunk/test/Transforms/Inline/inline-optsize.ll
> llvm/trunk/test/Transforms/Inline/inline_unreachable-2.ll
> llvm/trunk/test/Transforms/Inline/optimization-remarks-passed-yaml.ll
> llvm/trunk/test/Transforms/Inline/ptr-diff.ll
>
> Modified: llvm/trunk/lib/Analysis/InlineCost.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/
> Analysis/InlineCost.cpp?rev=286814&r1=286813&r2=286814&view=diff
> ============================================================
> ==================
> --- llvm/trunk/lib/Analysis/InlineCost.cpp (original)
> +++ llvm/trunk/lib/Analysis/InlineCost.cpp Mon Nov 14 05:14:41 2016
> @@ -1255,7 +1255,9 @@ bool CallAnalyzer::analyzeCall(CallSite
> Cost -= InlineConstants::InstrCost;
> }
> }
> -
> + // The call instruction also disappears after inlining.
> + Cost -= InlineConstants::InstrCost + InlineConstants::CallPenalty;
> +
> // If there is only one call of the function, and it has internal
> linkage,
> // the cost of inlining it drops dramatically.
> bool OnlyOneCallAndLocalLinkage =
>
> Modified: llvm/trunk/test/Transforms/Inline/alloca-bonus.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/
> Transforms/Inline/alloca-bonus.ll?rev=286814&r1=286813&r2=286814&view=diff
> ============================================================
> ==================
> --- llvm/trunk/test/Transforms/Inline/alloca-bonus.ll (original)
> +++ llvm/trunk/test/Transforms/Inline/alloca-bonus.ll Mon Nov 14 05:14:41
> 2016
> @@ -22,6 +22,7 @@ define void @inner1(i32 *%ptr) {
> %E = bitcast i32* %ptr to i8*
> %F = select i1 false, i32* %ptr, i32* @glbl
> call void @llvm.lifetime.start(i64 0, i8* %E)
> + call void @extern()
> ret void
> }
>
> @@ -42,6 +43,7 @@ define void @inner2(i32 *%ptr) {
> %E = bitcast i32* %ptr to i8*
> %F = select i1 false, i32* %ptr, i32* @glbl
> call void @llvm.lifetime.start(i64 0, i8* %E)
> + call void @extern()
> ret void
> }
>
> @@ -56,6 +58,7 @@ define void @outer3() {
> define void @inner3(i32 *%ptr, i1 %x) {
> %A = icmp eq i32* %ptr, null
> %B = and i1 %x, %A
> + call void @extern()
> br i1 %A, label %bb.true, label %bb.false
> bb.true:
> ; This block musn't be counted in the inline cost.
> @@ -97,6 +100,7 @@ define void @outer4(i32 %A) {
> define void @inner4(i32 *%ptr, i32 %A) {
> %B = getelementptr inbounds i32, i32* %ptr, i32 %A
> %C = icmp eq i32* %ptr, null
> + call void @extern()
> br i1 %C, label %bb.true, label %bb.false
> bb.true:
> ; This block musn't be counted in the inline cost.
> @@ -139,6 +143,7 @@ define void @outer5() {
> define void @inner5(i1 %flag, i32 *%ptr) {
> %A = load i32, i32* %ptr
> store i32 0, i32* %ptr
> + call void @extern()
> %C = getelementptr inbounds i32, i32* %ptr, i32 0
> br i1 %flag, label %if.then, label %exit
>
> @@ -153,3 +158,4 @@ exit:
> ret void
> }
>
> +declare void @extern()
>
> Modified: llvm/trunk/test/Transforms/Inline/inline-cold-callee.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/
> Transforms/Inline/inline-cold-callee.ll?rev=286814&r1=
> 286813&r2=286814&view=diff
> ============================================================
> ==================
> --- llvm/trunk/test/Transforms/Inline/inline-cold-callee.ll (original)
> +++ llvm/trunk/test/Transforms/Inline/inline-cold-callee.ll Mon Nov 14
> 05:14:41 2016
> @@ -9,7 +9,7 @@ define i32 @callee1(i32 %x) !prof !21 {
> %x1 = add i32 %x, 1
> %x2 = add i32 %x1, 1
> %x3 = add i32 %x2, 1
> -
> + call void @extern()
> ret i32 %x3
> }
>
> @@ -18,7 +18,7 @@ define i32 @callee2(i32 %x) !prof !22 {
> %x1 = add i32 %x, 1
> %x2 = add i32 %x1, 1
> %x3 = add i32 %x2, 1
> -
> + call void @extern()
> ret i32 %x3
> }
>
> @@ -32,6 +32,8 @@ define i32 @caller2(i32 %y1) !prof !22 {
> ret i32 %y3
> }
>
> +declare void @extern()
> +
> !llvm.module.flags = !{!1}
> !21 = !{!"function_entry_count", i64 100}
> !22 = !{!"function_entry_count", i64 1}
>
> Modified: llvm/trunk/test/Transforms/Inline/inline-cold.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/
> Transforms/Inline/inline-cold.ll?rev=286814&r1=286813&r2=286814&view=diff
> ============================================================
> ==================
> --- llvm/trunk/test/Transforms/Inline/inline-cold.ll (original)
> +++ llvm/trunk/test/Transforms/Inline/inline-cold.ll Mon Nov 14 05:14:41
> 2016
> @@ -17,6 +17,7 @@
> ; Function Attrs: nounwind readnone uwtable
> define i32 @simpleFunction(i32 %a) #0 {
> entry:
> + call void @extern()
> %a1 = load volatile i32, i32* @a
> %x1 = add i32 %a1, %a1
> %a2 = load volatile i32, i32* @a
> @@ -54,6 +55,7 @@ define i32 @ColdFunction(i32 %a) #1 {
> ; DEFAULT-LABEL: @ColdFunction
> ; DEFAULT: ret
> entry:
> + call void @extern()
> %a1 = load volatile i32, i32* @a
> %x1 = add i32 %a1, %a1
> %a2 = load volatile i32, i32* @a
> @@ -91,6 +93,7 @@ define i32 @ColdFunction2(i32 %a) #1 {
> ; DEFAULT-LABEL: @ColdFunction2
> ; DEFAULT: ret
> entry:
> + call void @extern()
> %a1 = load volatile i32, i32* @a
> %x1 = add i32 %a1, %a1
> %a2 = load volatile i32, i32* @a
> @@ -196,5 +199,6 @@ entry:
> ret i32 %add
> }
>
> +declare void @extern()
> attributes #0 = { nounwind readnone uwtable }
> attributes #1 = { nounwind cold readnone uwtable }
>
> Modified: llvm/trunk/test/Transforms/Inline/inline-hot-callee.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/
> Transforms/Inline/inline-hot-callee.ll?rev=286814&r1=
> 286813&r2=286814&view=diff
> ============================================================
> ==================
> --- llvm/trunk/test/Transforms/Inline/inline-hot-callee.ll (original)
> +++ llvm/trunk/test/Transforms/Inline/inline-hot-callee.ll Mon Nov 14
> 05:14:41 2016
> @@ -9,7 +9,7 @@ define i32 @callee1(i32 %x) !prof !21 {
> %x1 = add i32 %x, 1
> %x2 = add i32 %x1, 1
> %x3 = add i32 %x2, 1
> -
> + call void @extern()
> ret i32 %x3
> }
>
> @@ -18,7 +18,7 @@ define i32 @callee2(i32 %x) !prof !22 {
> %x1 = add i32 %x, 1
> %x2 = add i32 %x1, 1
> %x3 = add i32 %x2, 1
> -
> + call void @extern()
> ret i32 %x3
> }
>
> @@ -32,6 +32,8 @@ define i32 @caller2(i32 %y1) !prof !22 {
> ret i32 %y3
> }
>
> +declare void @extern()
> +
> !llvm.module.flags = !{!1}
> !21 = !{!"function_entry_count", i64 300}
> !22 = !{!"function_entry_count", i64 1}
>
> Modified: llvm/trunk/test/Transforms/Inline/inline-hot-callsite.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/
> Transforms/Inline/inline-hot-callsite.ll?rev=286814&r1=
> 286813&r2=286814&view=diff
> ============================================================
> ==================
> --- llvm/trunk/test/Transforms/Inline/inline-hot-callsite.ll (original)
> +++ llvm/trunk/test/Transforms/Inline/inline-hot-callsite.ll Mon Nov 14
> 05:14:41 2016
> @@ -9,7 +9,7 @@ define i32 @callee1(i32 %x) {
> %x1 = add i32 %x, 1
> %x2 = add i32 %x1, 1
> %x3 = add i32 %x2, 1
> -
> + call void @extern()
> ret i32 %x3
> }
>
> @@ -18,7 +18,7 @@ define i32 @callee2(i32 %x) {
> %x1 = add i32 %x, 1
> %x2 = add i32 %x1, 1
> %x3 = add i32 %x2, 1
> -
> + call void @extern()
> ret i32 %x3
> }
>
> @@ -32,6 +32,8 @@ define i32 @caller2(i32 %y1) {
> ret i32 %y3
> }
>
> +declare void @extern()
> +
> !llvm.module.flags = !{!1}
> !21 = !{!"branch_weights", i64 300}
> !22 = !{!"branch_weights", i64 1}
>
> Modified: llvm/trunk/test/Transforms/Inline/inline-optsize.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/
> Transforms/Inline/inline-optsize.ll?rev=286814&r1=
> 286813&r2=286814&view=diff
> ============================================================
> ==================
> --- llvm/trunk/test/Transforms/Inline/inline-optsize.ll (original)
> +++ llvm/trunk/test/Transforms/Inline/inline-optsize.ll Mon Nov 14
> 05:14:41 2016
> @@ -12,6 +12,7 @@
> ; This function should be larger than the inline threshold for -Oz (25),
> but
> ; smaller than the inline threshold for optsize (75).
> define i32 @inner() {
> + call void @extern()
> %a1 = load volatile i32, i32* @a
> %x1 = add i32 %a1, %a1
> %a2 = load volatile i32, i32* @a
> @@ -42,3 +43,5 @@ define i32 @outer2() minsize {
> %r = call i32 @inner()
> ret i32 %r
> }
> +
> +declare void @extern()
> \ No newline at end of file
>
> Modified: llvm/trunk/test/Transforms/Inline/inline_unreachable-2.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/
> Transforms/Inline/inline_unreachable-2.ll?rev=286814&
> r1=286813&r2=286814&view=diff
> ============================================================
> ==================
> --- llvm/trunk/test/Transforms/Inline/inline_unreachable-2.ll (original)
> +++ llvm/trunk/test/Transforms/Inline/inline_unreachable-2.ll Mon Nov 14
> 05:14:41 2016
> @@ -8,6 +8,7 @@ define void @caller(i32 %a, i1 %b) #0 {
> }
>
> define void @callee(i32 %a, i1 %b) {
> + call void @extern()
> call void asm sideeffect "", ""()
> br i1 %b, label %bb1, label %bb2
> bb1:
> @@ -17,3 +18,5 @@ bb2:
> call void asm sideeffect "", ""()
> ret void
> }
> +
> +declare void @extern()
> \ No newline at end of file
>
> Modified: llvm/trunk/test/Transforms/Inline/optimization-remarks-
> passed-yaml.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/
> Transforms/Inline/optimization-remarks-passed-
> yaml.ll?rev=286814&r1=286813&r2=286814&view=diff
> ============================================================
> ==================
> --- llvm/trunk/test/Transforms/Inline/optimization-remarks-passed-yaml.ll
> (original)
> +++ llvm/trunk/test/Transforms/Inline/optimization-remarks-passed-yaml.ll
> Mon Nov 14 05:14:41 2016
> @@ -12,7 +12,7 @@
> ; 4 return foo();
> ; 5 }
>
> -; CHECK: remark: /tmp/s.c:4:10: foo can be inlined into bar with
> cost={{[0-9]+}} (threshold={{[0-9]+}}) (hotness: 30)
> +; CHECK: remark: /tmp/s.c:4:10: foo can be inlined into bar with
> cost={{[0-9\-]+}} (threshold={{[0-9]+}}) (hotness: 30)
> ; CHECK-NEXT: remark: /tmp/s.c:4:10: foo inlined into bar (hotness: 30)
>
> ; YAML: --- !Analysis
> @@ -28,7 +28,7 @@
> ; YAML-NEXT: - Caller: bar
> ; YAML-NEXT: DebugLoc: { File: /tmp/s.c, Line: 3, Column: 0 }
> ; YAML-NEXT: - String: ' with cost='
> -; YAML-NEXT: - Cost: '{{[0-9]+}}'
> +; YAML-NEXT: - Cost: '{{[0-9\-]+}}'
> ; YAML-NEXT: - String: ' (threshold='
> ; YAML-NEXT: - Threshold: '{{[0-9]+}}'
> ; YAML-NEXT: - String: ')'
>
> Modified: llvm/trunk/test/Transforms/Inline/ptr-diff.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/
> Transforms/Inline/ptr-diff.ll?rev=286814&r1=286813&r2=286814&view=diff
> ============================================================
> ==================
> --- llvm/trunk/test/Transforms/Inline/ptr-diff.ll (original)
> +++ llvm/trunk/test/Transforms/Inline/ptr-diff.ll Mon Nov 14 05:14:41 2016
> @@ -4,7 +4,7 @@ target datalayout = "p:32:32-p1:64:64-p2
>
> define i32 @outer1() {
> ; CHECK-LABEL: @outer1(
> -; CHECK-NOT: call
> +; CHECK-NOT: call i32
> ; CHECK: ret i32
>
> %ptr = alloca i32
> @@ -15,6 +15,7 @@ define i32 @outer1() {
> }
>
> define i32 @inner1(i32* %begin, i32* %end) {
> + call void @extern()
> %begin.i = ptrtoint i32* %begin to i32
> %end.i = ptrtoint i32* %end to i32
> %distance = sub i32 %end.i, %begin.i
> @@ -43,6 +44,7 @@ define i32 @outer2(i32* %ptr) {
> }
>
> define i32 @inner2(i32* %begin, i32* %end) {
> + call void @extern()
> %begin.i = ptrtoint i32* %begin to i32
> %end.i = ptrtoint i32* %end to i32
> %distance = sub i32 %end.i, %begin.i
> @@ -60,6 +62,7 @@ else:
> ; The inttoptrs are free since it is a smaller integer to a larger
> ; pointer size
> define i32 @inttoptr_free_cost(i32 %a, i32 %b, i32 %c) {
> + call void @extern()
> %p1 = inttoptr i32 %a to i32 addrspace(1)*
> %p2 = inttoptr i32 %b to i32 addrspace(1)*
> %p3 = inttoptr i32 %c to i32 addrspace(1)*
> @@ -73,7 +76,7 @@ define i32 @inttoptr_free_cost(i32 %a, i
>
> define i32 @inttoptr_free_cost_user(i32 %begin, i32 %end) {
> ; CHECK-LABEL: @inttoptr_free_cost_user(
> -; CHECK-NOT: call
> +; CHECK-NOT: call i32
> %x = call i32 @inttoptr_free_cost(i32 %begin, i32 %end, i32 9)
> ret i32 %x
> }
> @@ -81,6 +84,7 @@ define i32 @inttoptr_free_cost_user(i32
> ; The inttoptrs have a cost since it is a larger integer to a smaller
> ; pointer size
> define i32 @inttoptr_cost_smaller_ptr(i32 %a, i32 %b, i32 %c) {
> + call void @extern()
> %p1 = inttoptr i32 %a to i32 addrspace(2)*
> %p2 = inttoptr i32 %b to i32 addrspace(2)*
> %p3 = inttoptr i32 %c to i32 addrspace(2)*
> @@ -94,8 +98,9 @@ define i32 @inttoptr_cost_smaller_ptr(i3
>
> define i32 @inttoptr_cost_smaller_ptr_user(i32 %begin, i32 %end) {
> ; CHECK-LABEL: @inttoptr_cost_smaller_ptr_user(
> -; CHECK: call
> +; CHECK: call i32
> %x = call i32 @inttoptr_cost_smaller_ptr(i32 %begin, i32 %end, i32 9)
> ret i32 %x
> }
>
> +declare void @extern()
> \ No newline at end of file
>
>
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