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Enhancement
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Resolution: Unresolved
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Low
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Code Generation Tools
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CODEGEN-11097
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ARM_20.2.7.LTS
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default
The attached file contains these lines ...
switch (switchInput)
{
case 1:
{
dummyStruct dummyInstance;
dummyFunction(x+11, &dummyInstance);
break;
}
case 2:
{
dummyStruct dummyInstance;
dummyFunction(x+12, &dummyInstance);
break;
}
/* 4 more switch cases that are similar */
dummyStruct is 400 bytes. Build it with version 18.1.8.LTS ...
% armcl --opt_level=0 --src_interlist file.c
Inspect file.asm. Here are some key lines ...
; The following local variables in dummyFunctionWithSwitchInside() will be grouped together ; to share stack space among distinct scoping blocks. References ; in the source interlisting will look like "O$1.s3_1.u4_2.s4_3.l4_4" or "&$O$O1+0". ; ; --offset-- --reference-- --variable-- ; ; 0 O$1.s3_1.u4_2.s4_3.l4_4 struct $$fake0 dummyInstance [file.c:54] ; 0 O$1.s3_1.u4_2.s4_5.l4_6 struct $$fake0 dummyInstance [file.c:47] ; 0 O$1.s3_1.u4_2.s4_7.l4_8 struct $$fake0 dummyInstance [file.c:40] ; 0 O$1.s3_1.u4_2.s4_9.l4_10 struct $$fake0 dummyInstance [file.c:33] ; 0 O$1.s3_1.u4_2.s4_11.l4_12 struct $$fake0 dummyInstance [file.c:26] ; 0 O$1.s3_1.u4_2.s4_13.l4_14 struct $$fake0 dummyInstance [file.c:19] <skip many lines> ;***************************************************************************** ;* FUNCTION NAME: dummyFunctionWithSwitchInside * ;* * ;* Regs Modified : A1,V9,SP,LR,SR * ;* Regs Used : A1,V9,SP,LR,SR * ;* Local Frame Size : 0 Args + 400 Auto + 4 Save = 404 byte * ;***************************************************************************** dummyFunctionWithSwitchInside:
Do the same thing with version 20.2.7.LTS. The comment about local variables grouped together is not present. The local frame size for the function is 2404 bytes, 6X more. Change to --opt_level=1, then stack usage is the same as 18.1.8.LTS with --opt_level=0.
