Introduce DebugCounter into PartiallyInlineLibCalls pass

[zhizhouy]

Summary

This patch introduces DebugCounter into PartiallyInlineLibCalls pass at per-transformation level.

It will provide an option to skip first n or stop after n transformations for the whole PartiallyInlineLibCalls pass.

This will make debug easier for the pass, also providing chance to do transformation level bisecting.

[zhizhouy]

Put test under X86/ directory, as -mtriple specified.

[zhizhouy]

ping for reviewing... thanks!

[davide]

LGTM. @eraman / @davidxl might have opinions on this.

[davidxl]

The counter name seems too long, how about dropping 'transform'.

[zhizhouy]

In D50093#1225257, @davidxl wrote:

The counter name seems too long, how about dropping 'transform'.

The idea is to add "-transform" after each DEBUT_TYPE name for passes so that we can do transformation level bisection using DebugCounter.
Just want to add this to unify all the names, but if you think it is too long, I think dropping it may also work.

[davidxl]

lgtm. I am not fixed on the naming either.

llvm/trunk/lib/Transforms/Scalar/PartiallyInlineLibCalls.cpp

 // does not need to set errno.
 //
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Transforms/Scalar/PartiallyInlineLibCalls.h"
 #include "llvm/Analysis/TargetLibraryInfo.h"
 #include "llvm/Analysis/TargetTransformInfo.h"
 #include "llvm/IR/IRBuilder.h"
+#include "llvm/Support/DebugCounter.h"
 #include "llvm/Transforms/Scalar.h"
 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
 
 using namespace llvm;
 
 #define DEBUG_TYPE "partially-inline-libcalls"
 
+DEBUG_COUNTER(PILCounter, "partially-inline-libcalls-transform",
+              "Controls transformations in partially-inline-libcalls");
 
 static bool optimizeSQRT(CallInst *Call, Function *CalledFunc,
                          BasicBlock &CurrBB, Function::iterator &BB,
                          const TargetTransformInfo *TTI) {
   // There is no need to change the IR, since backend will emit sqrt
   // instruction if the call has already been marked read-only.
   if (Call->onlyReadsMemory())
     return false;
 
+  if (!DebugCounter::shouldExecute(PILCounter))
+    return false;
+
   // Do the following transformation:
   //
   // (before)
   // dst = sqrt(src)
   //
   // (after)
   // v0 = sqrt_noreadmem(src) # native sqrt instruction.
   // [if (v0 is a NaN) || if (src < 0)]

llvm/trunk/test/Other/X86/debugcounter-partiallyinlinelibcalls.ll

+; REQUIRES: asserts
+; RUN: opt -S -debug-counter=partially-inline-libcalls-transform-skip=1,partially-inline-libcalls-transform-count=1 \
+; RUN:     -partially-inline-libcalls -mtriple=x86_64-unknown-linux-gnu < %s | FileCheck %s
+;; Test that, with debug counters on, we will skip the first optimization opportunity, perform next 1,
+;; and ignore all the others left.
+
+define float @f1(float %val) {
+; CHECK-LABEL: @f1(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[RES:%.*]] = tail call float @sqrtf(float [[VAL:%.*]])
+; CHECK-NEXT:    ret float [[RES:%.*]]
+entry:
+  %res = tail call float @sqrtf(float %val)
+  ret float %res
+}
+
+define float @f2(float %val) {
+; CHECK-LABEL: @f2(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[RES:%.*]] = tail call float @sqrtf(float [[VAL:%.*]]) #0
+; CHECK-NEXT:    [[TMP0:%.*]] = fcmp oge float [[VAL]], 0.000000e+00
+; CHECK-NEXT:    br i1 [[TMP0]], label [[ENTRY_SPLIT:%.*]], label [[CALL_SQRT:%.*]]
+; CHECK:       call.sqrt:
+; CHECK-NEXT:    [[TMP1:%.*]] = tail call float @sqrtf(float [[VAL]])
+; CHECK-NEXT:    br label [[ENTRY_SPLIT]]
+; CHECK:       entry.split:
+; CHECK-NEXT:    [[TMP2:%.*]] = phi float [ [[RES]], [[ENTRY:%.*]] ], [ [[TMP1]], [[CALL_SQRT]] ]
+; CHECK-NEXT:    ret float [[TMP2]]
+entry:
+  %res = tail call float @sqrtf(float %val)
+  ret float %res
+}
+
+define float @f3(float %val) {
+; CHECK-LABEL: @f3(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[RES:%.*]] = tail call float @sqrtf(float [[VAL:%.*]])
+; CHECK-NEXT:    ret float [[RES:%.*]]
+entry:
+  %res = tail call float @sqrtf(float %val)
+  ret float %res
+}
+
+declare float @sqrtf(float)