llvm-project

Commit Graph

Author	SHA1	Message	Date
Sanjay Patel	49aafec2e6	[InstCombine] don't try to evaluate instructions with >1 use (revert r324014) This example causes a compile-time explosion: define i16 @foo(i16 %in) { %x = zext i16 %in to i32 %a1 = mul i32 %x, %x %a2 = mul i32 %a1, %a1 %a3 = mul i32 %a2, %a2 %a4 = mul i32 %a3, %a3 %a5 = mul i32 %a4, %a4 %a6 = mul i32 %a5, %a5 %a7 = mul i32 %a6, %a6 %a8 = mul i32 %a7, %a7 %a9 = mul i32 %a8, %a8 %a10 = mul i32 %a9, %a9 %a11 = mul i32 %a10, %a10 %a12 = mul i32 %a11, %a11 %a13 = mul i32 %a12, %a12 %a14 = mul i32 %a13, %a13 %a15 = mul i32 %a14, %a14 %a16 = mul i32 %a15, %a15 %a17 = mul i32 %a16, %a16 %a18 = mul i32 %a17, %a17 %a19 = mul i32 %a18, %a18 %a20 = mul i32 %a19, %a19 %a21 = mul i32 %a20, %a20 %a22 = mul i32 %a21, %a21 %a23 = mul i32 %a22, %a22 %a24 = mul i32 %a23, %a23 %T = trunc i32 %a24 to i16 ret i16 %T } llvm-svn: 324276	2018-02-05 21:50:32 +00:00
Sanjay Patel	3343fcef86	[InstCombine] allow multi-use values in canEvaluate* if all uses are in 1 inst This is the enhancement suggested in D42536 to fix a shortcoming in regular InstCombine's canEvaluate* functionality. When we have multiple uses of a value, but they're all in one instruction, we can allow that expression to be narrowed or widened for the same cost as a single-use value. AFAICT, this can only matter for multiply: sub/and/or/xor/select would be simplified away if the operands are the same value; add becomes shl; shifts with a variable shift amount aren't handled. Differential Revision: https://reviews.llvm.org/D42739 llvm-svn: 324014	2018-02-01 21:55:53 +00:00
Sanjay Patel	fd58ade81c	[InstCombine] move related tests into the same file; NFC llvm-svn: 323882	2018-01-31 15:47:59 +00:00

Author

SHA1

Message

Date

Sanjay Patel

49aafec2e6

[InstCombine] don't try to evaluate instructions with >1 use (revert r324014)

This example causes a compile-time explosion:

define i16 @foo(i16 %in) {
  %x = zext i16 %in to i32
  %a1 = mul i32 %x, %x
  %a2 = mul i32 %a1, %a1
  %a3 = mul i32 %a2, %a2
  %a4 = mul i32 %a3, %a3
  %a5 = mul i32 %a4, %a4
  %a6 = mul i32 %a5, %a5
  %a7 = mul i32 %a6, %a6
  %a8 = mul i32 %a7, %a7
  %a9 = mul i32 %a8, %a8
  %a10 = mul i32 %a9, %a9
  %a11 = mul i32 %a10, %a10
  %a12 = mul i32 %a11, %a11
  %a13 = mul i32 %a12, %a12
  %a14 = mul i32 %a13, %a13
  %a15 = mul i32 %a14, %a14
  %a16 = mul i32 %a15, %a15
  %a17 = mul i32 %a16, %a16
  %a18 = mul i32 %a17, %a17
  %a19 = mul i32 %a18, %a18
  %a20 = mul i32 %a19, %a19
  %a21 = mul i32 %a20, %a20
  %a22 = mul i32 %a21, %a21
  %a23 = mul i32 %a22, %a22
  %a24 = mul i32 %a23, %a23
  %T = trunc i32 %a24 to i16
  ret i16 %T
}

 

llvm-svn: 324276

2018-02-05 21:50:32 +00:00

Sanjay Patel

3343fcef86

[InstCombine] allow multi-use values in canEvaluate* if all uses are in 1 inst

This is the enhancement suggested in D42536 to fix a shortcoming in 
regular InstCombine's canEvaluate* functionality.
When we have multiple uses of a value, but they're all in one instruction, we can 
allow that expression to be narrowed or widened for the same cost as a single-use 
value.

AFAICT, this can only matter for multiply: sub/and/or/xor/select would be simplified 
away if the operands are the same value; add becomes shl; shifts with a variable shift 
amount aren't handled.

Differential Revision: https://reviews.llvm.org/D42739

llvm-svn: 324014

2018-02-01 21:55:53 +00:00

Sanjay Patel

fd58ade81c

[InstCombine] move related tests into the same file; NFC

llvm-svn: 323882

2018-01-31 15:47:59 +00:00

3 Commits