In EM, fef splits a float into exponent and fraction. The old C code,
given an infinite float, got stuck in an infinite loop. The new
assembly code doesn't loop; it extracts the IEEE exponent.
This fixes code that tried to "addi SP, SP, 4" to drop a value that
was in a register, not on the real stack.
Add a rule to optimize "asp 4" (which becomes "loc 4" "ass") when
the value being dropped is already in a GPR.
When ncg fell back on this rule, it did emit the string "invalid" in
the assembly code and caused a syntax error in the assembler.
Adjust the stacking rules so we can stack LOCAL, CONST, and LABEL
without falling back on the "invalid" rule, and so we can stack them
when we have no free register except the scratch register.
GNU as has "la %r4,8(%r3)" as an alias for "addi %r4,%r3,8", meaning
to load the address of the thing at 8(%r3). Our 'la', now 'li32',
makes an addis/ori pair to load an immediate 32-bit value. For
example, "li32 r4,23456789" loads a big number.
Upon enabling the check, mach/powerpc/ncg/table fails to build as ncgg
gives many errors of "Previous rule impossible on empty stack". David
Given reported this problem in 2013:
https://sourceforge.net/p/tack/mailman/message/30814694/
Commit c93cb69 commented out the error in util/ncgg/cgg.y to disable
the Hall check. This commit enables it again. In ncgg, the Hall
check is checking that a rule is possible with an empty fake stack.
It would be possible if ncg can coerce the values from the real stack
to the fake stack. The powerpc table defined coercions from STACK to
{FS, %a} and {FD, %a}, but the Hall check didn't understand the
coercions and rejected each rule "with FS" or "with FD".
This commit removes the FS and FD tokens and adds a new group of FSREG
registers for single-precision floats, while keeping FREG registers
for double precision. The registers overlap, with each FSREG
containing one FREG, because it is the same register in PowerPC
hardware. FS tokens become FSREG registers and FD tokens become FREG
registers. The Hall check understands the coercions from STACK to
FSREG and FREG. The idea to define separate but overlapping registers
comes from the PDP-11 table (mach/pdp/ncg/table).
This commit also removes F0 from the FREG group. This is my attempt
to keep F0 off the fake stack, because one of the stacking rules uses
F0 as a scratch register (FSCRATCH).
Inspired by the sparc code (mach/sparc/libem/lar.s). My powerpc code
might still have bugs, but it's enough for examples/hilo.mod to work.
May need to 'make clean' or touch a build.lua file, so ackbuilder can
notice the new lar4.s and sar4.s files and build them.
calculated incorrectly because of overflow errors.
Replace it with an extended RELOPPC relocation which understands addis/ori
pairs; add an la pseudoop to the assembler which generates these and the
appropriate relocation. Make good.
--HG--
branch : dtrg-experimental-powerpc-branch
directories --- wrangling descr files was too hard. C programs can be built
for cpm, pc86, linux386, linux68k!
--HG--
branch : dtrg-buildsystem
rename : util/ack/build.mk => util/led/build.mk
rename : util/LLgen/build.mk => util/topgen/build.mk
