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author | Chris Lattner <sabre@nondot.org> | 2006-03-27 07:04:16 +0000 |
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committer | Chris Lattner <sabre@nondot.org> | 2006-03-27 07:04:16 +0000 |
commit | b86bd2cee25c15862247b4641700d448fbd0fa24 (patch) | |
tree | 00d5bad5ec49a4fe0107c5d2b61b4f34d203f8a5 /lib/Target/PowerPC/README.txt | |
parent | a0b3afbe14216884b66c867af23eb81f21399365 (diff) | |
download | llvm-b86bd2cee25c15862247b4641700d448fbd0fa24.tar.gz llvm-b86bd2cee25c15862247b4641700d448fbd0fa24.tar.bz2 llvm-b86bd2cee25c15862247b4641700d448fbd0fa24.tar.xz |
Split out altivec notes into their own README
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@27168 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/Target/PowerPC/README.txt')
-rw-r--r-- | lib/Target/PowerPC/README.txt | 54 |
1 files changed, 2 insertions, 52 deletions
diff --git a/lib/Target/PowerPC/README.txt b/lib/Target/PowerPC/README.txt index 410aa8a7ed..14a0bc124e 100644 --- a/lib/Target/PowerPC/README.txt +++ b/lib/Target/PowerPC/README.txt @@ -1,3 +1,5 @@ +//===- README.txt - Notes for improving PowerPC-specific code gen ---------===// + TODO: * gpr0 allocation * implement do-loop -> bdnz transform @@ -309,12 +311,6 @@ Generate lwbrx and other byteswapping load/store instructions when reasonable. ===-------------------------------------------------------------------------=== -Implement TargetConstantVec, and set up PPC to custom lower ConstantVec into -TargetConstantVec's if it's one of the many forms that are algorithmically -computable using the spiffy altivec instructions. - -===-------------------------------------------------------------------------=== - Compile this: int foo(int a) { @@ -502,11 +498,6 @@ This theoretically may help improve twolf slightly (used in dimbox.c:142?). ===-------------------------------------------------------------------------=== -Implement PPCInstrInfo::isLoadFromStackSlot/isStoreToStackSlot for vector -registers, to generate better spill code. - -===-------------------------------------------------------------------------=== - int foo(int N, int ***W, int **TK, int X) { int t, i; @@ -524,32 +515,6 @@ http://www.lcs.mit.edu/pubs/pdf/MIT-LCS-TM-600.pdf ===-------------------------------------------------------------------------=== -Altivec support. The first should be a single lvx from the constant pool, the -second should be a xor/stvx: - -void foo(void) { - int x[8] __attribute__((aligned(128))) = { 1, 1, 1, 1, 1, 1, 1, 1 }; - bar (x); -} - -#include <string.h> -void foo(void) { - int x[8] __attribute__((aligned(128))); - memset (x, 0, sizeof (x)); - bar (x); -} - -===-------------------------------------------------------------------------=== - -Altivec: Codegen'ing MUL with vector FMADD should add -0.0, not 0.0: -http://gcc.gnu.org/bugzilla/show_bug.cgi?id=8763 - -We need to codegen -0.0 vector efficiently (no constant pool load). - -When -ffast-math is on, we can use 0.0. - -===-------------------------------------------------------------------------=== - float foo(float X) { return (int)(X); } Currently produces: @@ -571,16 +536,6 @@ win only. ===-------------------------------------------------------------------------=== - Consider this: - v4f32 Vector; - v4f32 Vector2 = { Vector.X, Vector.X, Vector.X, Vector.X }; - -Since we know that "Vector" is 16-byte aligned and we know the element offset -of ".X", we should change the load into a lve*x instruction, instead of doing -a load/store/lve*x sequence. - -===-------------------------------------------------------------------------=== - We generate ugly code for this: void func(unsigned int *ret, float dx, float dy, float dz, float dw) { @@ -596,8 +551,3 @@ void func(unsigned int *ret, float dx, float dy, float dz, float dw) { ===-------------------------------------------------------------------------=== -There are a wide range of vector constants we can generate with combinations of -altivec instructions. For example, GCC does: t=vsplti*, r = t+t. - -===-------------------------------------------------------------------------=== - |