Allow -inline-threshold to override default (explicitly specified/derived from opt levels) threshold

[eraman]

Summary

Before r257832, the threshold used by SimpleInliner was explicitly specified or generated from opt levels and passed to the base class Inliner's constructor. There, it was first overridden by explicitly specified -inline-threshold. The refactoring in r257832 did not preserve this behavior for all opt levels. This change brings back the original behavior.

[chandlerc]

Thanks for fixing this! LGTM with the tweak below.

lib/Analysis/InlineCost.cpp

624–627 ↗

(On Diff #57867)

How about reversing the condition above? It seems much more natural to write

if (/* we have an explicit option */) {
  // use it...
} else {
  // use the thresholds
}

[eraman]

lib/Analysis/InlineCost.cpp

624–627 ↗

(On Diff #57867)

I've reversed the condition and also moved the comment at line 616 near the relevant code.

llvm/trunk/lib/Analysis/InlineCost.cpp

 
 void CallAnalyzer::updateThreshold(CallSite CS, Function &Callee) {
   // If no size growth is allowed for this inlining, set Threshold to 0.
   if (!allowSizeGrowth(CS)) {
     Threshold = 0;
     return;
   }
 
+  Function *Caller = CS.getCaller();
+  if (DefaultInlineThreshold.getNumOccurrences() > 0) {
+    // Explicitly specified -inline-threhold overrides the threshold passed to
+    // CallAnalyzer's constructor.
+    Threshold = DefaultInlineThreshold;
+  } else {
     // If -inline-threshold is not given, listen to the optsize and minsize
     // attributes when they would decrease the threshold.
-  Function *Caller = CS.getCaller();
-
-  if (!(DefaultInlineThreshold.getNumOccurrences() > 0)) {
     if (Caller->optForMinSize() && OptMinSizeThreshold < Threshold)
       Threshold = OptMinSizeThreshold;
     else if (Caller->optForSize() && OptSizeThreshold < Threshold)
       Threshold = OptSizeThreshold;
   }
 
   // If profile information is available, use that to adjust threshold of hot
   // and cold functions.

llvm/trunk/test/Transforms/Inline/inline-threshold.ll

+; Test that -inline-threshold overrides thresholds derived from opt levels.
+; RUN: opt < %s -O2 -inline-threshold=500 -S  | FileCheck %s
+; RUN: opt < %s -O3 -inline-threshold=500 -S  | FileCheck %s
+; RUN: opt < %s -Os -inline-threshold=500 -S  | FileCheck %s
+; RUN: opt < %s -Oz -inline-threshold=500 -S  | FileCheck %s
+
+@a = global i32 4
+
+define i32 @simpleFunction(i32 %a) #0 {
+entry:
+  %a1 = load volatile i32, i32* @a
+  %x1 = add i32 %a1,  %a1
+  %cmp = icmp eq i32 %a1, 0
+  br i1 %cmp, label %if.then, label %if.else
+if.then:
+  %a2 = load volatile i32, i32* @a
+  %x2_0 = add i32 %x1, %a2
+  br label %if.else
+if.else:
+  %x2 = phi i32 [ %x1, %entry ], [ %x2_0, %if.then ]
+  %a3 = load volatile i32, i32* @a
+  %x3 = add i32 %x2, %a3
+  %a4 = load volatile i32, i32* @a
+  %x4 = add i32 %x3, %a4
+  %a5 = load volatile i32, i32* @a
+  %x5 = add i32 %x4, %a5
+  %a6 = load volatile i32, i32* @a
+  %x6 = add i32 %x5, %a6
+  %a7 = load volatile i32, i32* @a
+  %x7 = add i32 %x6, %a7
+  %a8 = load volatile i32, i32* @a
+  %x8 = add i32 %x7, %a8
+  %a9 = load volatile i32, i32* @a
+  %x9 = add i32 %x8, %a9
+  %a10 = load volatile i32, i32* @a
+  %x10 = add i32 %x9, %a10
+  %a11 = load volatile i32, i32* @a
+  %x11 = add i32 %x10, %a11
+  %a12 = load volatile i32, i32* @a
+  %x12 = add i32 %x11, %a12
+  %a13 = load volatile i32, i32* @a
+  %x13 = add i32 %x12, %a13
+  %a14 = load volatile i32, i32* @a
+  %x14 = add i32 %x13, %a14
+  %a15 = load volatile i32, i32* @a
+  %x15 = add i32 %x14, %a15
+  %a16 = load volatile i32, i32* @a
+  %x16 = add i32 %x15, %a16
+  %a17 = load volatile i32, i32* @a
+  %x17 = add i32 %x16, %a17
+  %a18 = load volatile i32, i32* @a
+  %x18 = add i32 %x17, %a18
+  %a19 = load volatile i32, i32* @a
+  %x19 = add i32 %x18, %a19
+  %a20 = load volatile i32, i32* @a
+  %x20 = add i32 %x19, %a20
+  %a21 = load volatile i32, i32* @a
+  %x21 = add i32 %x20, %a21
+  %a22 = load volatile i32, i32* @a
+  %x22 = add i32 %x21, %a22
+  %a23 = load volatile i32, i32* @a
+  %x23 = add i32 %x22, %a23
+  %a24 = load volatile i32, i32* @a
+  %x24 = add i32 %x23, %a24
+  %a25 = load volatile i32, i32* @a
+  %x25 = add i32 %x24, %a25
+  %a26 = load volatile i32, i32* @a
+  %x26 = add i32 %x25, %a26
+  %a27 = load volatile i32, i32* @a
+  %x27 = add i32 %x26, %a27
+  %a28 = load volatile i32, i32* @a
+  %x28 = add i32 %x27, %a28
+  %a29 = load volatile i32, i32* @a
+  %x29 = add i32 %x28, %a29
+  %add = add i32 %x29, %a
+  ret i32 %add
+}
+
+; Function Attrs: nounwind readnone uwtable
+define i32 @bar(i32 %a) #0 {
+; CHECK-LABEL: @bar
+; CHECK-NOT: call i32 @simpleFunction(i32 6)
+; CHECK: ret
+entry:
+  %i = tail call i32 @simpleFunction(i32 6)
+  ret i32 %i
+}
+
+attributes #0 = { nounwind readnone uwtable }