[llvm] [CodeGen] Introduce Static Data Splitter pass (PR #122183)

[Wei Xiao via llvm-commits]

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@@ -0,0 +1,177 @@
+; -stats requires asserts
+; requires: asserts
+
+; Stop after 'finalize-isel' for simpler MIR, and lower the minimum number of
+; jump table entries so 'switch' needs fewer cases to generate a jump table.
+; RUN: llc -stop-after=finalize-isel -min-jump-table-entries=2 %s -o %t.mir
+; RUN: llc --run-pass=static-data-splitter -stats -x mir %t.mir -o - 2>&1 | FileCheck %s --check-prefix=STAT
+
+; Tests stat messages are expected.
+; TODO: Update test to verify section suffixes when target-lowering and assembler changes are implemented.
+; TODO: Also run static-data-splitter pass with -static-data-default-hotness=cold and check data section suffix.
+ 
+; STAT-DAG: 2 static-data-splitter - Number of cold jump tables seen
+; STAT-DAG: 2 static-data-splitter - Number of hot jump tables seen
+; STAT-DAG: 1 static-data-splitter - Number of jump tables with unknown hotness
+
+; In function @foo, the 2 switch instructions to jt0.* and jt2.* get lowered to hot jump tables,
+; and the 2 switch instructions to jt1.* and jt3.* get lowered to cold jump tables.
+
+; @func_without_profile doesn't have profiles. It's jump table hotness is unknown.
+
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+ at str.9 = private constant [7 x i8] c".str.9\00"
+ at str.10 = private constant [8 x i8] c".str.10\00"
+ at str.11 = private constant [8 x i8] c".str.11\00"
+
+ at case2 = private constant [7 x i8] c"case 2\00"
+ at case1 = private constant [7 x i8] c"case 1\00"
+ at default = private constant [8 x i8] c"default\00"
+ at jt3 = private constant [4 x i8] c"jt3\00"
+
+define i32 @foo(i32 %num) !prof !13 {
+entry:
+  %mod3 = sdiv i32 %num, 3
+  switch i32 %mod3, label %jt0.default [
+    i32 1, label %jt0.bb1
+    i32 2, label %jt0.bb2
+  ], !prof !14
+
+jt0.bb1:
+  call i32 @puts(ptr @case1)
+  br label %jt0.epilog
+
+jt0.bb2:
+  call i32 @puts(ptr @case2)
+  br label %jt0.epilog
+
+jt0.default:
+  call i32 @puts(ptr @default)
+  br label %jt0.epilog
+
+jt0.epilog:
+  %zero = icmp eq i32 %num, 0
+  br i1 %zero, label %hot, label %cold, !prof !15
+
+hot:
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williamweixiao wrote:

"hot:" --> "cold:"?

https://github.com/llvm/llvm-project/pull/122183