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...nsert useless instructions, let llc generate an assembly (.s) file, then use sed to replace the useless instructions with my special instructions. However, llc eliminates my useless instructions. ( Allocas and binary operators go away, volatile loads and stores change the register allocation. ) %mul_en = alloca i32 %2 = mul nsw i32 %y, %x %mul_dis = alloca i32 becomes... mul r12, r12, r0 Next I tried using llvm-dis and llvm-as to manually replace my useless instructions with a inline no-op in the .bc file. However, llc then moves the volatile no-op below the multiply. tail call void asm si...

On Dec 6, 2010, at 10:57 AM, John Criswell wrote: > On 12/6/10 11:39 AM, Andrew Lukefahr wrote: >> Hi, >> >> How would I disable dead code elimination in llc? Can that be done via the command line or do I need to modify llc's source? > > You can use llc --help-hidden to see a list of options. There are several -disable-xxx options that disable various code