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Add the commandline options -fprofile-instr-generate[=filename] and -profile-instr-use=filename -fprofile-instr-generate -- Add instrumentation on branches, switches, and function entry; uses LLVM's InstrProf pass. -- Link to profile runtime that writes instrumentation counters to a file. -fprofile-instr-use -- Read profile data from a file and apply branch weights to branches and switches, and annotate functions with entrycount in LLVM IR. -- Functions with low or high entrycount are marked with 'cold' or 'inlinehint'. The only statement type without PGO yet is "try-finally". A new pragma, `pragma(LDC_profile_instr, [ true | false ])`, is added to selectively disable/enable instrumentation of functions (granularity = whole functions). The runtime library ldc-profile-rt is a copy of LLVM compiler-rt lib/profile. It has to be exactly in-sync with the LLVM version, and thus we need a copy for each PGO-supported LLVM (>=3.7). import ldc.profile for a D interface to ldc-profile-rt (for example to reset execution counts after a program startup phase). The instrumentation data is mainly passed on to LLVM: function-entry counts and branch counts/probabilities. LDC marks functions as hot when "execution count is 30% of the maximum function execution count", and marks functions as cold if their count is 1% of maximum function execution count. The source of LLVM's llvm-profdata tool is hereby included in LDCs repository (different source for each LLVM version), and the binary is included in the install bin folder. The executable is named "ldc-profdata" to avoid clashing with llvm-profdata on the same machine. This is needed because profdata executable has to be in-sync with the LLVM version used to build LDC. Maintenance burden: for trunk LLVM, we have to keep ldc-profile-rt and llvm-profdata in sync. There is no diff with upstream; but because of active development there are the occasional API changes.
22 lines
647 B
D
22 lines
647 B
D
// Tests (the availability of) the runtime lib function to reset all profile counters.
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// RUN: %ldc -fprofile-instr-generate=%t.profraw -run %s \
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// RUN: && %profdata merge %t.profraw -o %t.profdata \
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// RUN: && %ldc -c -output-ll -of=%t2.ll -fprofile-instr-use=%t.profdata %s \
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// RUN: && FileCheck %s < %t2.ll
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extern(C) void foo(int N) {
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// CHECK-LABEL: define void @foo(
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// CHECK: br i1 %{{.*}}, label %{{.*}}, label %{{.*}}, !prof ![[FOO:[0-9]+]]
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if (N) {}
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}
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// CHECK-LABEL: define i32 @_Dmain(
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void main() {
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import ldc.profile;
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foo(0);
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resetAll();
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foo(1);
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}
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// CHECK: ![[FOO]] = !{!"branch_weights", i32 2, i32 1}
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