Add the cold attribute to error-reporting call sites

Generally speaking, control flow paths with error reporting calls are cold.
So far, error reporting calls are calls to perror and calls to fprintf,
fwrite, etc. with stderr as the stream. This can be extended in the future.

The primary motivation is to improve block placement (the cold attribute
affects the static branch prediction heuristics).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@194943 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 77 insertions, 0 deletions

diff --git a/test/Transforms/InstCombine/err-rep-cold.ll b/test/Transforms/InstCombine/err-rep-cold.ll
new file mode 100644
index 0000000..0cbafc4
--- /dev/null
+++ b/test/Transforms/InstCombine/err-rep-cold.ll
@@ -0,0 +1,77 @@
+; Test the static branch probability heuristics for error-reporting functions.
+; RUN: opt < %s -instcombine -S | FileCheck %s
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+%struct._IO_FILE = type { i32, i8*, i8*, i8*, i8*, i8*, i8*, i8*, i8*, i8*, i8*, i8*, %struct._IO_marker*, %struct._IO_FILE*, i32, i32, i64, i16, i8, [1 x i8], i8*, i64, i8*, i8*, i8*, i8*, i64, i32, [20 x i8] }
+%struct._IO_marker = type { %struct._IO_marker*, %struct._IO_FILE*, i32 }
+
+@stdout = external global %struct._IO_FILE*
+@stderr = external global %struct._IO_FILE*
+@.str = private unnamed_addr constant [13 x i8] c"an error: %d\00", align 1
+@.str1 = private unnamed_addr constant [9 x i8] c"an error\00", align 1
+
+define i32 @test1(i32 %a) #0 {
+; CHECK-LABEL: @test1
+entry:
+  %cmp = icmp sgt i32 %a, 8
+  br i1 %cmp, label %if.then, label %return
+
+if.then:                                          ; preds = %entry
+  %0 = load %struct._IO_FILE** @stderr, align 8
+  %call = tail call i32 (%struct._IO_FILE*, i8*, ...)* @fprintf(%struct._IO_FILE* %0, i8* getelementptr inbounds ([13 x i8]* @.str, i64 0, i64 0), i32 %a) #1
+  br label %return
+
+; CHECK: %call = tail call i32 (%struct._IO_FILE*, i8*, ...)* @fprintf(%struct._IO_FILE* %0, i8* getelementptr inbounds ([13 x i8]* @.str, i64 0, i64 0), i32 %a) #[[AT1:[0-9]+]]
+
+return:                                           ; preds = %entry, %if.then
+  %retval.0 = phi i32 [ 1, %if.then ], [ 0, %entry ]
+  ret i32 %retval.0
+}
+
+declare i32 @fprintf(%struct._IO_FILE* nocapture, i8* nocapture readonly, ...) #1
+
+define i32 @test2(i32 %a) #0 {
+; CHECK-LABEL: @test2
+entry:
+  %cmp = icmp sgt i32 %a, 8
+  br i1 %cmp, label %if.then, label %return
+
+if.then:                                          ; preds = %entry
+  %0 = load %struct._IO_FILE** @stderr, align 8
+  %1 = tail call i64 @fwrite(i8* getelementptr inbounds ([9 x i8]* @.str1, i64 0, i64 0), i64 8, i64 1, %struct._IO_FILE* %0)
+  br label %return
+
+; CHECK: tail call i64 @fwrite(i8* getelementptr inbounds ([9 x i8]* @.str1, i64 0, i64 0), i64 8, i64 1, %struct._IO_FILE* %0) #[[AT2:[0-9]+]]
+
+return:                                           ; preds = %entry, %if.then
+  %retval.0 = phi i32 [ 1, %if.then ], [ 0, %entry ]
+  ret i32 %retval.0
+}
+
+declare i64 @fwrite(i8* nocapture, i64, i64, %struct._IO_FILE* nocapture) #1
+
+define i32 @test3(i32 %a) #0 {
+; CHECK-LABEL: @test3
+entry:
+  %cmp = icmp sgt i32 %a, 8
+  br i1 %cmp, label %if.then, label %return
+
+if.then:                                          ; preds = %entry
+  %0 = load %struct._IO_FILE** @stdout, align 8
+  %1 = tail call i64 @fwrite(i8* getelementptr inbounds ([9 x i8]* @.str1, i64 0, i64 0), i64 8, i64 1, %struct._IO_FILE* %0)
+  br label %return
+
+; CHECK-NOT: tail call i64 @fwrite(i8* getelementptr inbounds ([9 x i8]* @.str1, i64 0, i64 0), i64 8, i64 1, %struct._IO_FILE* %0) #[[AT2]]
+
+return:                                           ; preds = %entry, %if.then
+  %retval.0 = phi i32 [ 1, %if.then ], [ 0, %entry ]
+  ret i32 %retval.0
+}
+
+attributes #0 = { nounwind uwtable }
+attributes #1 = { nounwind }
+
+; CHECK: attributes #[[AT1]] = { cold nounwind }
+; CHECK: attributes #[[AT2]] = { cold }
+