Revisions to Why does GCC generate 15-20% faster code if I optimize for size instead of speed?

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edit approved May 7, 2017 at 21:46

newbie

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Here is are the results for time ./test 0 0 on several processors (user time reported):

Here is are results for time ./test 0 0 on several processors (user time reported):

Here are the results for time ./test 0 0 on several processors (user time reported):

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edited Apr 10, 2017 at 20:12

Toby Speight

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Update: on Ivy Bridge-based Core i3 three versions of gcc (4.6.4, 4.7.3, and 4.8.1) produce binaries with significantly different performance, but the assembly code has only subtle variations. So far, I have no explaination toexplanation of this fact.

Update: on Ivy Bridge-based Core i3 three versions of gcc (4.6.4, 4.7.3, and 4.8.1) produce binaries with significantly different performance, but the assembly code has only subtle variations. So far, I have no explaination to this fact.

Update: on Ivy Bridge-based Core i3 three versions of gcc (4.6.4, 4.7.3, and 4.8.1) produce binaries with significantly different performance, but the assembly code has only subtle variations. So far, I have no explanation of this fact.

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edited Oct 20, 2013 at 5:40

Marat Dukhan

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Processor (System-on-Chip) Compiler Time (-O2) Time (-Os) Fastest AMD Opteron 8350 gcc-4.8.1 0.704s 0.896s -O2 AMD FX-6300 gcc-4.8.1 0.392s 0.340s -Os AMD E2-1800 gcc-4.7.2 0.740s 0.832s -O2 Intel Xeon E5405 gcc-4.8.1 0.603s 0.804s -O2 Intel Xeon E5-2603 gcc-4.4.7 1.121s 1.122s - Intel Core i3-3217U gcc-4.6.4 0.709s 0.709s - Intel Core i3-3217U gcc-4.7.3 0.708s 0.822s -O2 Intel Core i3-3217U gcc-4.8.1 0.708s 0.944s -O2 Intel Core i7-4770K gcc-4.8.1 0.296s 0.288s -Os Intel Atom 330 gcc-4.8.1 2.003s 2.007s -O2 ARM 1176JZF-S (Broadcom BCM2835) gcc-4.6.3 3.470s 3.480s -O2 ARM Cortex-A8 (TI OMAP DM3730) gcc-4.6.3 2.727s 2.727s - ARM Cortex-A9 (TI OMAP 4460) gcc-4.6.3 1.648s 1.648s - ARM Cortex-A9 (Samsung Exynos 4412) gcc-4.6.3 1.250s 1.250s - ARM Cortex-A15 (Samsung Exynos 5250) gcc-4.7.2 0.700s 0.700s - Qualcomm Snapdragon APQ8060A  gcc-4.8 1.53s 1.52s -Os

Processor (System-on-Chip) Compiler Time (-O2) Time (-Os) Fastest AMD FX-6300 gcc-4.8.1 0.392s 0.340s -Os AMD E2-1800 gcc-4.7.2 0.740s 0.832s -O2 Intel Xeon E5405 gcc-4.8.1 0.603s 0.804s -O2 Intel Xeon E5-2603 gcc-4.4.7 1.121s 1.122s - Intel Core i3-3217U gcc-4.6.4 0.709s 0.709s - Intel Core i3-3217U gcc-4.7.3 0.708s 0.822s -O2 Intel Core i3-3217U gcc-4.8.1 0.708s 0.944s -O2 Intel Core i7-4770K gcc-4.8.1 0.296s 0.288s -Os Intel Atom 330 gcc-4.8.1 2.003s 2.007s -O2 ARM 1176JZF-S (Broadcom BCM2835) gcc-4.6.3 3.470s 3.480s -O2 ARM Cortex-A8 (TI OMAP DM3730) gcc-4.6.3 2.727s 2.727s - ARM Cortex-A9 (TI OMAP 4460) gcc-4.6.3 1.648s 1.648s - ARM Cortex-A9 (Samsung Exynos 4412) gcc-4.6.3 1.250s 1.250s - ARM Cortex-A15 (Samsung Exynos 5250) gcc-4.7.2 0.700s 0.700s -

Processor (System-on-Chip) Compiler Time (-O2) Time (-Os) Fastest AMD Opteron 8350 gcc-4.8.1 0.704s 0.896s -O2 AMD FX-6300 gcc-4.8.1 0.392s 0.340s -Os AMD E2-1800 gcc-4.7.2 0.740s 0.832s -O2 Intel Xeon E5405 gcc-4.8.1 0.603s 0.804s -O2 Intel Xeon E5-2603 gcc-4.4.7 1.121s 1.122s - Intel Core i3-3217U gcc-4.6.4 0.709s 0.709s - Intel Core i3-3217U gcc-4.7.3 0.708s 0.822s -O2 Intel Core i3-3217U gcc-4.8.1 0.708s 0.944s -O2 Intel Core i7-4770K gcc-4.8.1 0.296s 0.288s -Os Intel Atom 330 gcc-4.8.1 2.003s 2.007s -O2 ARM 1176JZF-S (Broadcom BCM2835) gcc-4.6.3 3.470s 3.480s -O2 ARM Cortex-A8 (TI OMAP DM3730) gcc-4.6.3 2.727s 2.727s - ARM Cortex-A9 (TI OMAP 4460) gcc-4.6.3 1.648s 1.648s - ARM Cortex-A9 (Samsung Exynos 4412) gcc-4.6.3 1.250s 1.250s - ARM Cortex-A15 (Samsung Exynos 5250) gcc-4.7.2 0.700s 0.700s - Qualcomm Snapdragon APQ8060A  gcc-4.8 1.53s 1.52s -Os