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| author | Christian Krinitsin <mail@krinitsin.com> | 2025-07-06 16:43:19 +0000 |
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| committer | Christian Krinitsin <mail@krinitsin.com> | 2025-07-06 16:43:19 +0000 |
| commit | 238ec2b7cc1557d6f34c33cc482e4d0cd3e266dd (patch) | |
| tree | cd8a1b75ba7b3543eb7fe6857f408e7be4d9fd0b /results/classifier/gemma3:27b/instruction/1793119 | |
| parent | 96049c939b1916d80532630d63c14e04d5244f1d (diff) | |
| download | emulator-bug-study-238ec2b7cc1557d6f34c33cc482e4d0cd3e266dd.tar.gz emulator-bug-study-238ec2b7cc1557d6f34c33cc482e4d0cd3e266dd.zip | |
add results
Diffstat (limited to 'results/classifier/gemma3:27b/instruction/1793119')
| -rw-r--r-- | results/classifier/gemma3:27b/instruction/1793119 | 32 |
1 files changed, 32 insertions, 0 deletions
diff --git a/results/classifier/gemma3:27b/instruction/1793119 b/results/classifier/gemma3:27b/instruction/1793119 new file mode 100644 index 00000000..9990b2c6 --- /dev/null +++ b/results/classifier/gemma3:27b/instruction/1793119 @@ -0,0 +1,32 @@ + + + +Wrong floating-point emulation on AArch64 with FPCR set to zero + +On AArch64, with FPCR set to Zero (i.e., FPU set to IEEE-754 compliant mode), floating-point emulation does not produce the same results as real hardware (e.g., Raspberry Pi 3 with AArch64 Linux). + +I attached a sample that reproduces the issue. It divides `x` by `y` and puts the result in `r`. The expected result of the operation is `q`. + +Output on real hardware: +========================================================= +fpcr = 0x07000000. +x = 0x03250f416dcdc6d0. y = 0x00029f4e5837c977. r = 0x7ff0000000000000. q = 0x43300fde9cbcf023. +fpcr = 0x00000000. +x = 0x03250f416dcdc6d0. y = 0x00029f4e5837c977. r = 0x43300fde9cbcf023. q = 0x43300fde9cbcf023. +========================================================= + +Notice that after setting FPCR to zero, `r` equals `q`. + +Output on qemu 3.0.0 (Linux user-mode emulation): +========================================================= +fpcr = 0x07000000. +x = 0x03250f416dcdc6d0. y = 0x00029f4e5837c977. r = 0x7ff0000000000000. q = 0x43300fde9cbcf023. +fpcr = 0x00000000. +x = 0x03250f416dcdc6d0. y = 0x00029f4e5837c977. r = 0x43300fde9cbcf024. q = 0x43300fde9cbcf023. +========================================================= + +Notice that after setting FPCR to zero, `r` is not equal to `q`. + +Also notice that, using another proprietary operating system, the same issue arises between a real board and QEMU. This might be an issue in emulation of the AArch64 instruction "fdiv". + +Build command line: aarch64-linux-gnu-gcc -static -O0 -o sample1 sample1.c \ No newline at end of file |