[LLVMdev] [PATCH] Fix arm sbfx/ubfx generation

[David Conrad]

Hi,

Currently llvm can generate an invalid sbfx/ubfx op, for instance when  
compiling encoder/analyse.c in x264 (I'll reduce this to a test case  
if needed):

clang -O3  -Wall -I. -isysroot=/Developer/Platforms/iPhoneOS.platform/ 
Developer/SDKs/iPhoneOS3.0.sdk -Qunused-arguments -mno-thumb -mdynamic- 
no-pic -arch armv7 -mcpu=cortex-a8 -mfpu=neon -mfloat-abi=softfp - 
DHAVE_ARMV6 -DHAVE_ARMV6T2 -DHAVE_NEON -DARCH_ARM -DSYS_MACOSX - 
DHAVE_PTHREAD -s -fomit-frame-pointer -I/usr/X11/include  -c -o  
encoder/analyse.o encoder/analyse.c
/var/folders/WC/WCQfew6LEaqrFEF+j4W8CE+++TI/-Tmp-/cc-4koben.s: 
10000:immediate value out of range -- `sbfx r12,r12,#-2,#31'
/var/folders/WC/WCQfew6LEaqrFEF+j4W8CE+++TI/-Tmp-/cc-4koben.s: 
10041:immediate value out of range -- `sbfx r12,r0,#-2,#31'
/var/folders/WC/WCQfew6LEaqrFEF+j4W8CE+++TI/-Tmp-/cc-4koben.s: 
10336:immediate value out of range -- `sbfx r2,r8,#-2,#31'
/var/folders/WC/WCQfew6LEaqrFEF+j4W8CE+++TI/-Tmp-/cc-4koben.s: 
10362:immediate value out of range -- `sbfx r2,r6,#-2,#31'
/var/folders/WC/WCQfew6LEaqrFEF+j4W8CE+++TI/-Tmp-/cc-4koben.s: 
13229:immediate value out of range -- `sbfx r0,r0,#-2,#31'
/var/folders/WC/WCQfew6LEaqrFEF+j4W8CE+++TI/-Tmp-/cc-4koben.s: 
13235:immediate value out of range -- `sbfx r0,r3,#-2,#31'
clang: error: assembler command failed with exit code 1 (use -v to see  
invocation)
make: *** [encoder/analyse.o] Error 1

LSB isn't checked to ensure it's non-negative. In addition, LSB +  
Width cannot be >32, since it reduces to (Srl_imm - Shl_imm) + (32 -  
Srl_imm) == 32 - Shl_imm, and it was already assert()ed that 0 <  
Shl_imm < 32. So that check is just replaced by if (LSB < 0)

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