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Use 32-bit XORRegReg to zero registers on x64 #19236

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0xdaryl opened this issue Mar 27, 2024 · 0 comments · Fixed by #19320
Closed

Use 32-bit XORRegReg to zero registers on x64 #19236

0xdaryl opened this issue Mar 27, 2024 · 0 comments · Fixed by #19320
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arch:x86 bits:64 comp:jit good first issue Good for newcomers

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@0xdaryl
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0xdaryl commented Mar 27, 2024

When XORRegReg is used to zero a register on x64, the 32-bit operand form should be used because the upper 32-bits of the result are automatically zero extended. This will save a REX prefix on each of these instructions (1 byte savings).

Sweep through the x86 code generator looking at where XORRegReg or XOR8RegReg is used for the purpose of zeroing a register and ensure it uses XOR4RegReg instead. I found a few on inspection.

OpenJ9 companion issue to eclipse/omr#7295
R2steven pushed a commit to R2steven/openj9 that referenced this issue Apr 5, 2024
Use 32-bit XOR to zero registers in x64
a522534 
Swept through x86 codegen and replaced XORRegReg with XOR4RegReg when used to zero a register

Closes eclipse-openj9#19236
Signed-off-by: Ryan Stevens <restevens52+eclipse@gmail.com>
@R2steven R2steven mentioned this issue Apr 12, 2024
Closed
R2steven added a commit to R2steven/openj9 that referenced this issue Apr 12, 2024
@R2steven
Use 32-bit XOR to zero registers in x64
0ba6cf1 
Swept through x86 codegen and replaced XORRegReg with XOR4RegReg when used to zero a register

Closes eclipse-openj9#19236
Signed-off-by: Ryan Stevens <restevens52@gmail.com>
@R2steven R2steven mentioned this issue Apr 12, 2024
Merged
R2steven added a commit to R2steven/openj9 that referenced this issue Apr 25, 2024
@R2steven
Fix missing cases in AMD64JNILinkage
c4dc97a 
converted XORRegReg() to XOR4RegReg in AMD64JNILinkage.cpp

closes eclipse-openj9#19236
Sighed-off-by: Ryan Stevens restevens52@gmail.com
R2steven added a commit to R2steven/openj9 that referenced this issue May 6, 2024
@R2steven
Use 32-bit XOR to zero registers in x64
f240f9e 
Swept through x86 codegen and replaced XORRegReg with XOR4RegReg when used to zero a register

Closes eclipse-openj9#19236
Signed-off-by: Ryan Stevens <restevens52@gmail.com>
R2steven added a commit to R2steven/openj9 that referenced this issue May 6, 2024
@R2steven
Use 32-bit XOR to zero registers in x64
c359140 
Swept through x86 codegen and replaced XORRegReg with XOR4RegReg when used to zero a register

Closes eclipse-openj9#19236
Signed-off-by: Ryan Stevens <restevens52@gmail.com>
R2steven added a commit to R2steven/openj9 that referenced this issue May 6, 2024
@R2steven
Use 32-bit XOR to zero registers in x64
9a71c58 
Swept through x86 codegen and replaced XORRegReg with XOR4RegReg when used to zero a register

Closes eclipse-openj9#19236
Signed-off-by: Ryan Stevens <restevens52@gmail.com>

Fix missing cases in AMD64JNILinkage

converted XORRegReg() to XOR4RegReg in AMD64JNILinkage.cpp

closes eclipse-openj9#19236
Signed-off-by: Ryan Stevens <restevens52@gmail.com>
R2steven added a commit to R2steven/openj9 that referenced this issue May 6, 2024
@R2steven
Use 32-bit XOR to zero registers in x64
37f4869 
Swept through x86 codegen and replaced XORRegReg with XOR4RegReg when used to zero a register

Fix missing cases in AMD64JNILinkage
converted XORRegReg() to XOR4RegReg in AMD64JNILinkage.cpp

closes eclipse-openj9#19236
Signed-off-by: Ryan Stevens <restevens52@gmail.com>
AswathySK pushed a commit to AswathySK/openj9 that referenced this issue Jun 4, 2024
@R2steven @AswathySK
Use 32-bit XOR to zero registers in x64
c83ad01 
Swept through x86 codegen and replaced XORRegReg with XOR4RegReg when used to zero a register

Fix missing cases in AMD64JNILinkage
converted XORRegReg() to XOR4RegReg in AMD64JNILinkage.cpp

closes eclipse-openj9#19236
Signed-off-by: Ryan Stevens <restevens52@gmail.com>
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Use 32-bit XOR to zero registers in x64 R2steven/openj9
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