From: James Molloy <james.molloy@arm.com>
Date: Mon, 14 Nov 2016 11:14:41 +0000 (+0000)
Subject: [InlineCost] Remove skew when calculating call costs
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=a52fb282daed4f2217ce55d40bf8028002a1041a;p=llvm

[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();
  }

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@286814 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Analysis/InlineCost.cpp b/lib/Analysis/InlineCost.cpp
index d820069e6ce..6c3525fad4e 100644
--- a/lib/Analysis/InlineCost.cpp
+++ b/lib/Analysis/InlineCost.cpp
@@ -1255,7 +1255,9 @@ bool CallAnalyzer::analyzeCall(CallSite CS) {
       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 =
diff --git a/test/Transforms/Inline/alloca-bonus.ll b/test/Transforms/Inline/alloca-bonus.ll
index 649fac909fb..76a59ff6915 100644
--- a/test/Transforms/Inline/alloca-bonus.ll
+++ b/test/Transforms/Inline/alloca-bonus.ll
@@ -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()
diff --git a/test/Transforms/Inline/inline-cold-callee.ll b/test/Transforms/Inline/inline-cold-callee.ll
index 8e202e91ffa..cfd56c28173 100644
--- a/test/Transforms/Inline/inline-cold-callee.ll
+++ b/test/Transforms/Inline/inline-cold-callee.ll
@@ -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}
diff --git a/test/Transforms/Inline/inline-cold.ll b/test/Transforms/Inline/inline-cold.ll
index b3c134538a4..93d2569d87a 100644
--- a/test/Transforms/Inline/inline-cold.ll
+++ b/test/Transforms/Inline/inline-cold.ll
@@ -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 }
diff --git a/test/Transforms/Inline/inline-hot-callee.ll b/test/Transforms/Inline/inline-hot-callee.ll
index 7a04b517bf6..59d44bbb501 100644
--- a/test/Transforms/Inline/inline-hot-callee.ll
+++ b/test/Transforms/Inline/inline-hot-callee.ll
@@ -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}
diff --git a/test/Transforms/Inline/inline-hot-callsite.ll b/test/Transforms/Inline/inline-hot-callsite.ll
index 46993f49cc6..cc18fe6099c 100644
--- a/test/Transforms/Inline/inline-hot-callsite.ll
+++ b/test/Transforms/Inline/inline-hot-callsite.ll
@@ -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}
diff --git a/test/Transforms/Inline/inline-optsize.ll b/test/Transforms/Inline/inline-optsize.ll
index 7e62245fd3f..c7cd9b3189d 100644
--- a/test/Transforms/Inline/inline-optsize.ll
+++ b/test/Transforms/Inline/inline-optsize.ll
@@ -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
diff --git a/test/Transforms/Inline/inline_unreachable-2.ll b/test/Transforms/Inline/inline_unreachable-2.ll
index 57f090effc5..cc038c9b720 100644
--- a/test/Transforms/Inline/inline_unreachable-2.ll
+++ b/test/Transforms/Inline/inline_unreachable-2.ll
@@ -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
diff --git a/test/Transforms/Inline/optimization-remarks-passed-yaml.ll b/test/Transforms/Inline/optimization-remarks-passed-yaml.ll
index 1e173342d8b..f532a164857 100644
--- a/test/Transforms/Inline/optimization-remarks-passed-yaml.ll
+++ b/test/Transforms/Inline/optimization-remarks-passed-yaml.ll
@@ -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: ')'
diff --git a/test/Transforms/Inline/ptr-diff.ll b/test/Transforms/Inline/ptr-diff.ll
index 728f3793ee2..d4647b7891b 100644
--- a/test/Transforms/Inline/ptr-diff.ll
+++ b/test/Transforms/Inline/ptr-diff.ll
@@ -4,7 +4,7 @@ target datalayout = "p:32:32-p1:64:64-p2:16:16-n16:32:64"
 
 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, i32 %b, i32 %c) {
 
 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 %begin, i32 %end) {
 ; 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(i32 %a, i32 %b, i32 %c) {
 
 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