[llvm] Add DIExpression::foldConstantMath to CoroSplit (PR #107933)

[Shubham Sandeep Rastogi via llvm-commits]

https://github.com/rastogishubham created https://github.com/llvm/llvm-project/pull/107933

The CoroSplit pass has it's own salvageDebugInfo implementation and it's DIExpressions do not get folded. Add a call to DIExpression::foldConstantMath in the CoroSplit pass to reduce the size of those DIExpressions.

[The compile time tracker shows no significant increase in compile time either.](https://llvm-compile-time-tracker.com/compare.php?from=bdf02249e7f8f95177ff58c881caf219699acb98&to=e1c1c1759c06bc4c42f79eebdb0e3cd45219cef4&stat=instructions:u)



>From e1c1c1759c06bc4c42f79eebdb0e3cd45219cef4 Mon Sep 17 00:00:00 2001
From: Shubham Sandeep Rastogi <srastogi22 at apple.com>
Date: Mon, 9 Sep 2024 15:33:08 -0700
Subject: [PATCH] Add DIExpression::foldConstantMath to CoroSplit

The CoroSplit pass has it's own salvageDebugInfo implementation and
it's DIExpressions do not get folded. Add a call to
DIExpression::foldConstantMath in the CoroSplit pass to reduce the size
of those DIExpressions.
---
 llvm/lib/Transforms/Coroutines/CoroFrame.cpp       | 1 +
 llvm/test/Transforms/Coroutines/swift-async-dbg.ll | 8 ++++----
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/llvm/lib/Transforms/Coroutines/CoroFrame.cpp b/llvm/lib/Transforms/Coroutines/CoroFrame.cpp
index 7a631a646f3f8b..c0cbebc91e7371 100644
--- a/llvm/lib/Transforms/Coroutines/CoroFrame.cpp
+++ b/llvm/lib/Transforms/Coroutines/CoroFrame.cpp
@@ -2659,6 +2659,7 @@ salvageDebugInfoImpl(SmallDenseMap<Argument *, AllocaInst *, 4> &ArgToAllocaMap,
     Expr = DIExpression::prepend(Expr, DIExpression::DerefBefore);
   }
 
+  Expr = Expr->foldConstantMath();
   return {{*Storage, *Expr}};
 }
 
diff --git a/llvm/test/Transforms/Coroutines/swift-async-dbg.ll b/llvm/test/Transforms/Coroutines/swift-async-dbg.ll
index 8c90fcbe19bc5e..2cd0f1c42b730b 100644
--- a/llvm/test/Transforms/Coroutines/swift-async-dbg.ll
+++ b/llvm/test/Transforms/Coroutines/swift-async-dbg.ll
@@ -30,7 +30,7 @@ define swifttailcc void @coroutineA(ptr swiftasync %arg) !dbg !48 {
 ; CHECK-LABEL: define {{.*}} @coroutineA(
 ; CHECK-SAME:    ptr swiftasync %[[frame_ptr:.*]])
 ; CHECK:      #dbg_declare(ptr %[[frame_ptr]], {{.*}} !DIExpression(
-; CHECK-SAME:                   DW_OP_plus_uconst, 16, DW_OP_plus_uconst, 8)
+; CHECK-SAME:                   DW_OP_plus_uconst, 24)
 ; CHECK:      #dbg_value(ptr %[[frame_ptr]], {{.*}} !DIExpression(
 ; CHECK-SAME:                 DW_OP_plus_uconst, 16, DW_OP_deref)
 ; CHECK:      call {{.*}} @swift_task_switch
@@ -49,7 +49,7 @@ define swifttailcc void @coroutineA(ptr swiftasync %arg) !dbg !48 {
 ; CHECK-LABEL: define {{.*}} @coroutineATY0_(
 ; CHECK-SAME:    ptr swiftasync %[[frame_ptr:.*]])
 ; CHECK:      #dbg_declare(ptr %[[frame_ptr]], {{.*}} !DIExpression(
-; CHECK-SAME:                   DW_OP_LLVM_entry_value, 1, DW_OP_plus_uconst, 16, DW_OP_plus_uconst, 8)
+; CHECK-SAME:                   DW_OP_LLVM_entry_value, 1, DW_OP_plus_uconst, 24)
 ; CHECK:      #dbg_value(ptr %[[frame_ptr]], {{.*}} !DIExpression(
 ; CHECK-SAME:                 DW_OP_LLVM_entry_value, 1, DW_OP_plus_uconst, 16, DW_OP_deref)
 ; CHECK:      #dbg_value(!DIArgList(ptr %[[frame_ptr]], i32 %{{.*}}), {{.*}} !DIExpression(
@@ -70,7 +70,7 @@ define swifttailcc void @coroutineA(ptr swiftasync %arg) !dbg !48 {
 ; CHECK-SAME:    ptr swiftasync %[[frame_ptr:.*]])
 ; Note the extra level of indirection that shows up here!
 ; CHECK:      #dbg_declare(ptr %[[frame_ptr]], {{.*}} !DIExpression(
-; CHECK-SAME:                   DW_OP_LLVM_entry_value, 1, DW_OP_deref, DW_OP_plus_uconst, 16, DW_OP_plus_uconst, 8)
+; CHECK-SAME:                   DW_OP_LLVM_entry_value, 1, DW_OP_deref, DW_OP_plus_uconst, 24)
 ; CHECK:      #dbg_value(ptr %[[frame_ptr]], {{.*}} !DIExpression(
 ; CHECK-SAME:                 DW_OP_LLVM_entry_value, 1, DW_OP_deref, DW_OP_plus_uconst, 16, DW_OP_deref)
 ; CHECK:      call {{.*}} @swift_task_switch
@@ -85,7 +85,7 @@ define swifttailcc void @coroutineA(ptr swiftasync %arg) !dbg !48 {
 ; CHECK-LABEL: define {{.*}} @coroutineATY2_(
 ; CHECK-SAME:    ptr swiftasync %[[frame_ptr:.*]])
 ; CHECK:      #dbg_declare(ptr %[[frame_ptr]], {{.*}} !DIExpression(
-; CHECK-SAME:                   DW_OP_LLVM_entry_value, 1, DW_OP_plus_uconst, 16, DW_OP_plus_uconst, 8)
+; CHECK-SAME:                   DW_OP_LLVM_entry_value, 1, DW_OP_plus_uconst, 24)
 }
 
 ; Everything from here on is just support code for the coroutines.