| Summary: |
[4.3/4.4 Regression] optabs expands rotate using wrong mode |
| Product: |
gcc
|
Reporter: |
Andy Hutchinson <hutchinsonandy> |
| Component: |
middle-end | Assignee: |
Not yet assigned to anyone <unassigned> |
| Status: |
RESOLVED
FIXED
|
|
|
| Severity: |
normal
|
CC: |
eric.weddington, gcc-bugs, hutchinsonandy, sezeroz
|
| Priority: |
P3
|
Keywords: |
wrong-code |
| Version: |
4.4.2 | |
|
| Target Milestone: |
4.5.0 | |
|
|
Host:
|
i686-pc-linux-gnu
|
Target:
|
avr-unknown-none
|
|---|
|
Build:
|
|
Known to work:
|
4.2.3 4.5.0
|
|---|
|
Known to fail:
|
4.3.3 4.4.2
|
Last reconfirmed:
|
2009-10-17 15:04:59
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|---|
I have been adding rotate capability to AVR port and have come this bug in optabs.c: expand_binop() This occurs during a rotate expansion. For example target = op0 rotated by op1 In the particular situation (code extract below) it tries a reverse rotate of (bits - op1). Where this expression is then expanded into an integer, a negation or subtraction depending on type of op1 and target. The expansion of the subtraction is using the mode of the target - it should be using the mode of op1. The mode of the rotation amount need not be the same as the target. target:DI = Op0:DI rotate op1:HI In my testcase it is not and I get asserts latter in simplfy_rtx with the mismatched inner/outer modes. The negation mode looks equally wrong. I found this on testcase 20010226-1.c with gcc 4.42 (line 55) - however, it would appear to be on 4.5 and perhaps earlier versions. Revision 126370 added this particular code to optabs.c in July 2007 /* If we were trying to rotate, and that didn't work, try rotating the other direction before falling back to shifts and bitwise-or. */ if (((binoptab == rotl_optab && optab_handler (rotr_optab, mode)->insn_code != CODE_FOR_nothing) || (binoptab == rotr_optab && optab_handler (rotl_optab, mode)->insn_code != CODE_FOR_nothing)) && mclass == MODE_INT) { optab otheroptab = (binoptab == rotl_optab ? rotr_optab : rotl_optab); rtx newop1; unsigned int bits = GET_MODE_BITSIZE (mode); if (CONST_INT_P (op1)) newop1 = GEN_INT (bits - INTVAL (op1)); else if (targetm.shift_truncation_mask (mode) == bits - 1) newop1 = negate_rtx (mode, op1); else newop1 = expand_binop (mode, sub_optab, GEN_INT (bits), op1, NULL_RTX, unsignedp, OPTAB_DIRECT);