[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

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 =

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()

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}

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 }

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}

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}

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()

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()

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: ')'

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()