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transform: allocate the correct amount of bytes in an alloca

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When I wrote the code originally, I didn't know about SetAlignment so I
hacked a way around it by allocating [...]uintptr types. However, this
allocates a few too many bytes in some cases.
This commit changes this to only allocate the space that we actually
need.

The code size effect is mixed, but generally positive. The combined
average is reduced by 0.27% with more programs being reduced in size
than are increasing in size.
This commit is contained in:
Ayke van Laethem
2021-12-08 22:09:49 +01:00
committed by Ron Evans
parent 08d0dc0d25
commit ef8c1a187d
2 changed files with 33 additions and 16 deletions
Download Patch File Download Diff File Expand all files Collapse all files
transform/testdata/allocs.out.ll
Vendored
+12 -12
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@@ -6,17 +6,17 @@ target triple = "armv7m-none-eabi"
declare nonnull i8* @runtime.alloc(i32, i8*)
define void @testInt() {
%stackalloc.alloca = alloca [1 x i32], align 4
store [1 x i32] zeroinitializer, [1 x i32]* %stackalloc.alloca, align 4
%stackalloc = bitcast [1 x i32]* %stackalloc.alloca to i32*
%stackalloc.alloca = alloca [4 x i8], align 4
store [4 x i8] zeroinitializer, [4 x i8]* %stackalloc.alloca, align 4
%stackalloc = bitcast [4 x i8]* %stackalloc.alloca to i32*
store i32 5, i32* %stackalloc, align 4
ret void
}
define i16 @testArray() {
%stackalloc.alloca = alloca [2 x i32], align 4
store [2 x i32] zeroinitializer, [2 x i32]* %stackalloc.alloca, align 4
%stackalloc = bitcast [2 x i32]* %stackalloc.alloca to i16*
%stackalloc.alloca = alloca [6 x i8], align 2
store [6 x i8] zeroinitializer, [6 x i8]* %stackalloc.alloca, align 2
%stackalloc = bitcast [6 x i8]* %stackalloc.alloca to i16*
%1 = getelementptr i16, i16* %stackalloc, i32 1
store i16 5, i16* %1, align 2
%2 = getelementptr i16, i16* %stackalloc, i32 2
@@ -39,9 +39,9 @@ define void @testEscapingCall2() {
}
define void @testNonEscapingCall() {
%stackalloc.alloca = alloca [1 x i32], align 4
store [1 x i32] zeroinitializer, [1 x i32]* %stackalloc.alloca, align 4
%stackalloc = bitcast [1 x i32]* %stackalloc.alloca to i32*
%stackalloc.alloca = alloca [4 x i8], align 4
store [4 x i8] zeroinitializer, [4 x i8]* %stackalloc.alloca, align 4
%stackalloc = bitcast [4 x i8]* %stackalloc.alloca to i32*
%1 = call i32* @noescapeIntPtr(i32* %stackalloc)
ret void
}
@@ -54,12 +54,12 @@ define i32* @testEscapingReturn() {
define void @testNonEscapingLoop() {
entry:
%stackalloc.alloca = alloca [1 x i32], align 4
%stackalloc.alloca = alloca [4 x i8], align 4
br label %loop
loop: ; preds = %loop, %entry
store [1 x i32] zeroinitializer, [1 x i32]* %stackalloc.alloca, align 4
%stackalloc = bitcast [1 x i32]* %stackalloc.alloca to i32*
store [4 x i8] zeroinitializer, [4 x i8]* %stackalloc.alloca, align 4
%stackalloc = bitcast [4 x i8]* %stackalloc.alloca to i32*
%0 = call i32* @noescapeIntPtr(i32* %stackalloc)
%1 = icmp eq i32* null, %0
br i1 %1, label %loop, label %end